review vs research papers

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Review vs. Research Articles

How can you tell if you are looking at a research paper, review paper or a systematic review  examples and article characteristics are provided below to help you figure it out., research papers.

A research article describes a study that was performed by the article’s author(s). It explains the methodology of the study, such as how data was collected and analyzed, and clarifies what the results mean. Each step of the study is reported in detail so that other researchers can repeat the experiment.

To determine if a paper is a research article, examine its wording. Research articles describe actions taken by the researcher(s) during the experimental process. Look for statements like “we tested,” “I measured,” or “we investigated.” Research articles also describe the outcomes of studies. Check for phrases like “the study found” or “the results indicate.” Next, look closely at the formatting of the article. Research papers are divided into sections that occur in a particular order: abstract, introduction, methods, results, discussion, and references.

Let's take a closer look at this research paper by Bacon et al. published in the International Journal of Hypertension :

Review Papers

Review articles do not describe original research conducted by the author(s). Instead, they give an overview of a specific subject by examining previously published studies on the topic. The author searches for and selects studies on the subject and then tries to make sense of their findings. In particular, review articles look at whether the outcomes of the chosen studies are similar, and if they are not, attempt to explain the conflicting results. By interpreting the findings of previous studies, review articles are able to present the current knowledge and understanding of a specific topic.

Since review articles summarize the research on a particular topic, students should read them for background information before consulting detailed, technical research articles. Furthermore, review articles are a useful starting point for a research project because their reference lists can be used to find additional articles on the subject.

Let's take a closer look at this review paper by Bacon et al. published in Sports Medicine :

Systematic Review Papers

A systematic review is a type of review article that tries to limit the occurrence of bias. Traditional, non-systematic reviews can be biased because they do not include all of the available papers on the review’s topic; only certain studies are discussed by the author. No formal process is used to decide which articles to include in the review. Consequently, unpublished articles, older papers, works in foreign languages, manuscripts published in small journals, and studies that conflict with the author’s beliefs can be overlooked or excluded. Since traditional reviews do not have to explain the techniques used to select the studies, it can be difficult to determine if the author’s bias affected the review’s findings.

Systematic reviews were developed to address the problem of bias. Unlike traditional reviews, which cover a broad topic, systematic reviews focus on a single question, such as if a particular intervention successfully treats a medical condition. Systematic reviews then track down all of the available studies that address the question, choose some to include in the review, and critique them using predetermined criteria. The studies are found, selected, and evaluated using a formal, scientific methodology in order to minimize the effect of the author’s bias. The methodology is clearly explained in the systematic review so that readers can form opinions about the quality of the review.

Let's take a closer look this systematic review paper by Vigano et al. published in Lancet Oncology :

Finding Review and Research Papers in PubMed

Many databases have special features that allow the searcher to restrict results to articles that match specific criteria. In other words, only articles of a certain type will be displayed in the search results. These “limiters” can be useful when searching for research or review articles. PubMed has a limiter for article type, which is located on the left sidebar of the search results page. This limiter can filter the search results to show only review articles.

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Research and Review Papers: The Key Differences

Research and review papers are two of the most common types of scholarly works that contribute to a field’s progress. Despite their similarities, these two forms of writing have distinct differences in structure, content, purpose, and tone. This article will explore the distinctions between research papers and reviews by exploring each type separately before comparing them in terms of academic rigor, length, methodology used for data gathering or analysis (if applicable), formal language use in referencing sources as well as citing references throughout the paper itself. Finally we will discuss ways students can effectively differentiate between research papers versus review documents when engaging with either form while completing assignments or producing new work themselves.

1. Introduction: Investigating the Difference Between Research and Review Papers

2. types of scholarly papers commonly used in academia, 3. characteristics that distinguish a research paper from a review paper, 4. the role of original research within each type of paper, 5. structural elements unique to each kind of academic writing, 6. tips for differentiating between the two types when analyzing content, 7. conclusion: examining how understanding the differences can help students write better quality papers.

Exploring the Differences between Research and Review Papers The academic world is often abuzz with discourse on research and review papers. These two types of writing are distinct in their approach, structure, content and purpose. To begin, a research paper represents an original piece of work that involves comprehensive study into existing knowledge. It requires students to use scientific methodology to investigate topics by collecting data through experimentation or observation; it should then be analyzed thoroughly before any conclusions can be drawn. On the other hand, a review paper is more focused on existing literature: synthesizing different authors’ views together while pointing out various similarities/differences among them. The main goal is usually critiquing previous theories from an objective point-of-view rather than offering new ones for consideration.

In terms of composition style and formatting preferences – both types require rigorous proofreading but there are some nuances that distinguish one from another as well: research papers will typically feature introduction + body (with sections such as background info., materials & methods etc.)+ conclusion; reviews may also have this organization yet rely heavily on summarization techniques due to its nature of being secondary material based only off previously published works by others in the field at hand! Furthermore — references cited within research papers need to meet certain criteria whereas those included within review pieces can vary greatly depending upon particular topic under examination – so always remember these subtle distinctions when considering which type you’re trying write next time around!

When pursuing an academic career, it is important to be familiar with the different types of scholarly papers used in academia. Different areas of research often require different paper styles depending on the specifics and focus of the project. Here are two types that tend to be widely accepted.

Research papers and review papers are two distinct types of scholarly works, each with its own purpose. The primary difference between the two is that research papers aim to provide new insight into a given topic whereas review papers build upon existing knowledge by summarizing what has already been published on the subject.

• Purpose : Research paper typically focus on identifying or verifying an answer to a specific question or hypothesis through rigorous investigation of evidence from primary sources (e.g., empirical studies). Review articles, however, tend to evaluate and synthesize pre-existing information for readers’ benefit.
• Scope : While research articles often examine only one aspect of their chosen topic in great detail, reviews take a wider angle by combining multiple studies together under one umbrella theme. Reviews also incorporate other forms of data such as interviews, surveys and anecdotal accounts to offer more comprehensive insights.

Original research papers and review papers are two distinct types of academic writing, with each having its own set of specific requirements. Original research is the backbone behind any great paper as it allows for new facts to be discovered or revealed while providing an opportunity for interpretation and analysis. On the other hand, a review paper synthesizes previous work from multiple sources into one cohesive argument that can help provide greater insight into an issue.

• It provides a starting point by establishing evidence-based information on which to build further knowledge.
• It offers readers the chance to view your original insights in light of existing theories and literature.
• It establishes credibility when peers recognize contributions you have made based on careful investigation

Reviews allow researchers to combine ideas from several different studies into one more comprehensive overview .                       They enable readers—such as those studying at higher levels who lack time —to quickly familiarize themselves with current findings without needing additional primary data collection or synthesis .

Essay Writing

The hallmark of essay writing is the way it structures ideas into a coherent argument. Essays usually consist of an introduction, several body paragraphs and a conclusion. Each section can take up multiple pages as students may need to elaborate on key points or evidence from research studies to back up their point of view. It is essential that each paragraph logically transitions in order for readers to make sense out of them when they are read together.

Research Paper Writing A research paper requires much more extensive analysis than an essay does. In addition to discussing related literature, these papers often involve collecting data through surveys or experiments and providing detailed descriptions about study results and conclusions reached based on this information. Research papers may include charts, tables and diagrams in addition to written text which help illustrate any scientific processes or observations found during the course of investigations conducted by the student author.

• Compare & Contrast : A review paper will cover different aspects but unlike a research paper it won’t include gathering new data.

Distinguishing Content Analysis Types:

Analyzing content can be a daunting task without an understanding of the two types: research papers and review papers. Research papers are typically written to explain new results, while review papers offer insights on existing literature. Although both types focus on evidence-based arguments in their analysis, it is possible to differentiate between them through several tips.

Firstly, research paper should have a hypothesis that was tested with data or experiments. It is likely this work will include quantitative methods such as statistics or qualitative techniques like interviews; these elements make it easier to identify a paper’s type as one of empirical research rather than just opinion pieces. In contrast, review articles summarize what has already been published and assess current trends within the field instead of examining hypotheses.

• When researching scientific topics especially check if figures are included.

In general, primary sources from other researchers are necessary for creating original claims whereas reviews usually cite many secondary sources because they do not involve original findings.

• Consider which facts appear most frequently when analyzing whether something is a primary source.

Comprehending the Distinctions

Aspiring academic writers should be aware that research papers and review papers are fundamentally different. While each requires in-depth analysis, synthesis of existing literature, careful referencing and citation of sources, a research paper is intended to present original findings while a review paper provides an overview and synthesis of relevant sources. Therefore, an understanding of these distinctions can help students write better quality papers.

When writing either type of paper it’s important for students to understand their objectives. A successful research paper will require more time spent conducting independent investigation or experimentation than would a review paper which typically involves summarizing the conclusions drawn by other scholars on the topic being studied. Furthermore when formulating arguments in either type student must take into consideration how best to use evidence from reliable scholarly sources as support for their views.

• Research Papers: Involves gathering new data through primary investigation or experiments.
• Review Paper: Involves synthesising existing literature on particular subject.

In conclusion knowledge about both types can assist student authors craft higher caliber assignments as well as give them confidence that they have chosen appropriate approaches in tackling difficult topics within academia .

As a final thought, it is important to understand the differences between research and review papers in order to make sure that any work produced reflects an appropriate level of academic rigour. Research papers are typically more complex than reviews because they require original findings through empirical or theoretical study, whereas reviews rely on synthesizing existing literature from multiple sources. Knowing the key distinctions between these two types of writing can help ensure accuracy, clarity and ultimately success for both students and professionals alike when producing written works for submission or publication.

Review Paper vs. Research Paper: Main Differences

Doing a paper is difficult, so learn the difference between a review paper vs. research paper, to determine which one is ideal for you.

A research paper and a review paper are two very specific types of papers. They have different motives, goals, and prerequisites. The elements found in research papers and review papers differ. The research paper is based on originality, therefore the paper takes into consideration the author’s original research, whereas the review paper is founded on an existing collection of knowledge. 

This article will walk you through the main differences between a review paper vs. research paper, allowing you to correctly determine which one is ideal for your work.

What is a review paper?

A review paper project tries to provide readers with an overview of an existing collection of knowledge by reviewing a book or an article and examining its content, structure, style, and statements. Reviews, such as peer reviews, can be used to examine and assess the work of other authors, rating the work by comparing it to the work of others. A review article is frequently written for a large readership, which is why it is usually brief. 

Review papers can be classified into three types:

• Narrative: a collection of and attempt to communicate all known information about a certain topic. It is based on research that has previously been completed and published. 
• Meta-analysis: a method of comparing and combining the findings of past research studies. It is done routinely to evaluate the efficacy of a particular initiative or method of treatment.
• Systematic: a search of all known scientific information on a topic to find a solution to a specific issue or problem. 

What is a research paper?

A research paper entails writing on research that has been performed by themselves, usually something new and done mostly from scratch since it has to be original research. It incorporates the research parameters, as well as the assessment, interpretation and important findings of the research. 

Writing a research paper involves several phases and different aspects, such as: selecting a topic, developing a hypothesis, conducting research, testing the hypothesis, drawing conclusions, and publishing a paper supporting or denying the hypothesis. 

Review paper vs. Research paper

Now that you have a basic understanding of both sorts of papers, it is time to compare and contrast the main differences between review paper vs. research paper.

These are the main differences, however, there may be others:

• A research paper is usually more detailed and thorough than a review paper.
• A research paper is usually peer-reviewed, but a review paper is not always.
• In general, a research paper is more formal than a review paper.
• A research paper’s tone is normally objective, but a review paper’s tone can be more subjective.
• A research paper is normally written in APA style, however, a review paper may be written in a different format.

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Differences Between Review Paper and Research Paper

A research paper includes original work while a review paper includes the summary of existing work which explains or solves a specific problem. 

An integral part of a PhD dissertation or thesis is writing a research and review article, besides writing a thesis, proposal and synopsis. In addition, one also has to publish an article in a peer-reviewed journal which is indeed a tougher task, right!

Writing is an indispensable part of the doctorate degree and has significant value in honoring the same degree. A student when becoming a PhD candidate has to write a thesis statement, research proposal, synopsis of the doctorate, thesis, research article and review article, in chronological order.

If one fails to do so, they can’t get a degree. And that’s why writing is important. Nonetheless, students face problems while writing either research or review articles. 

Supportive evidence suggests that students actually don’t know the basic and major differences between either so fail to publish both article types. 

In the present piece of content, I will explain the importance of a review and research article as well as the differences between both. I am hoping that this article will add value to your knowledge and help you in your PhD. 

Stay tuned. 

What is a Review Paper? 

What is a research paper, review vs research paper: differences, research article vs review article- similarities:, wrapping up: .

A review chapter or review articles add value to the thesis as well as existing knowledge. Universities are usually recommended to write and publish it. From students’ perspectives, review writing frightens them. 

However, from a supervisors’ perspective, it should be precise, concise and nearly perfect. 

Review writing is a tedious, frustrating and time-consuming process that needs special attention. The reason why it should be nearly perfect is that it supports researchers’ original work. 

Technically, the review article comprises a summary of the existing research in a structured manner. Normally, it addresses the original research work and solves the existing problem by literature. 

However, it can’t solve any existing problem, it doesn’t need wet-lab experimentation. It only shows the existing state of understanding of a topic. Notedly, an expert of the subject, experienced person, professor and professional scientist can usually write a review. 

A research paper/article contributes original research or work of a researcher on the present topic, usually includes web lab work. Much like the review, a research article should be published in a peer-reviewed journal too. 

Research article writing takes too much time as it includes research work additionally. Comprehensive writing is required to explain the materials & methods section and results & outcomes while the elaborative explanation is sufficient to introduce a topic. 

Structurally a typical research article or paper has an introduction or background, Materials & Methods, Results & discussion and conclusion. 

Depending upon the requirement of the journal and the depth or concentration of the research, the length of the article may vary, however, ordinarily is between 2 to 8 pages. 

Much like the review article, an abstract and a list of references must be included in the article. 

In summary, the research paper provides new knowledge in the relevant field and solves an existing problem by it. 

Now quickly move to the important part of this article, what are the differences between the review and research paper? 

A review article is certainly a comprehensive, in-depth and extensively well-written piece of information covering summaries of already present knowledge. While the research article constitutes an elaborative introduction of the topic and an in-depth explanation of how the research was conducted. It contributes new knowledge.

A review is written based on the already existing information and so considered as a secondary source of information, while the research paper has original research work supported by already existing sources. 

In terms of length, a review article has an in-depth explanation and so are longer, normally, 10 to 20 pages whilst the research article has an elaborative explanation and to the point information on the problem, usually ranging from 2 to 8 pages.

The review article addresses the problem whilst the research article solves the problem, certainly. 

The conclusion of the review article supports the already present findings while the result of the research article is supported by the existing research work. 

The purpose of writing a research paper is to critically analyze already existing or previous work in the form of short summaries. And restricted to a specific topic. 

On the other side, the research article includes the author’s own work in detail

Structurally, the review article has a single heading or sometimes a conclusion at the end of the article whilst the research article has sections like an introduction to the topic, materials & methods, results, discussion and final interpretation. 

Steps in review article writing are,

• Topic finding 
• Searching relevant sources
• Summarising each source 
• Correlating them with the topic or problem
• Concluding the research.

Steps in research article writing are,

• Choosing a problem or gap in present findings
• Sample collection, experimentation and wet lab work
• Finding, collecting and organizing the data
• Correlating it with the present knowledge
• Stating results 
• Final interpretation.

Normally, a subject expert or experienced person can write a review article while any student, or person having the original research work can write a research article.

The review article defines or clarifies a problem, explains it by compiling previous investigations and suggests problem-solving strategies or options. On the other hand, the research article has an original problem-solving statement supported by various chapters and previous research. 

So the review article suggests possible outcomes to fill the knowledge gap while the research article provides evidence and new knowledge on how to fill the gap. 

Summary: 

Either document has been written for a different purpose which solves almost the same objective. Fortunately, there are several similarities in writing a research or review article. Hera re some,

Both have in-text citations, a references page, an abstract and contributors. Both also need a final conclusion too in order to address or solve a problem. 

Research or review articles can be submitted or published in peer-reviewed journals. 

Both require educational, professional, informal and research writing skills. 

Importantly, both articles must be plagiarism-free, copying isn’t recommended. 

Every PhD student must have written at least a single review and research article during their research or doctoral tenure to get an award. Achieving a successful publication needs critical writing skills and original research or findings. 

The major difference between either is that the review article has summed information that directs one towards solving a problem and so does not include original work. 

Whilst the research article actually proposes a way to solve a problem and so has original work.  

Dr. Tushar Chauhan is a Scientist, Blogger and Scientific-writer. He has completed PhD in Genetics. Dr. Chauhan is a PhD coach and tutor.

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• Scholarly Journals and Popular Magazines
• Differences in Research, Review, and Opinion Articles

Scholarly Journals and Popular Magazines: Differences in Research, Review, and Opinion Articles

• Where Do I Start?
• How Do I Find Peer-Reviewed Articles?
• How Do I Compare Periodical Types?
• Where Can I find More Information?

Research Articles, Reviews, and Opinion Pieces

Scholarly or research articles are written for experts in their fields. They are often peer-reviewed or reviewed by other experts in the field prior to publication. They often have terminology or jargon that is field specific. They are generally lengthy articles. Social science and science scholarly articles have similar structures as do arts and humanities scholarly articles. Not all items in a scholarly journal are peer reviewed. For example, an editorial opinion items can be published in a scholarly journal but the article itself is not scholarly. Scholarly journals may include book reviews or other content that have not been peer reviewed.

Empirical Study: (Original or Primary) based on observation, experimentation, or study. Clinical trials, clinical case studies, and most meta-analyses are empirical studies.

Review Article: (Secondary Sources) Article that summarizes the research in a particular subject, area, or topic. They often include a summary, an literature reviews, systematic reviews, and meta-analyses.

Clinical case study (Primary or Original sources): These articles provide real cases from medical or clinical practice. They often include symptoms and diagnosis.

Clinical trials ( Health Research): Th ese articles are often based on large groups of people. They often include methods and control studies. They tend to be lengthy articles.

Opinion Piece:  An opinion piece often includes personal thoughts, beliefs, or feelings or a judgement or conclusion based on facts. The goal may be to persuade or influence the reader that their position on this topic is the best.

Book review: Recent review of books in the field. They may be several pages but tend to be fairly short. 

Social Science and Science Research Articles

The majority of social science and physical science articles include

• Journal Title and Author
• Abstract 
• Introduction with a hypothesis or thesis
• Literature Review
• Methods/Methodology
• Results/Findings

Arts and Humanities Research Articles

In the Arts and Humanities, scholarly articles tend to be less formatted than in the social sciences and sciences. In the humanities, scholars are not conducting the same kinds of research experiments, but they are still using evidence to draw logical conclusions.  Common sections of these articles include:

• an Introduction
• Discussion/Conclusion
• works cited/References/Bibliography

Research versus Review Articles

• 6 Article types that journals publish: A guide for early career researchers
• INFOGRAPHIC: 5 Differences between a research paper and a review paper
• Michigan State University. Empirical vs Review Articles
• UC Merced Library. Empirical & Review Articles
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Types of journal articles

It is helpful to familiarise yourself with the different types of articles published by journals. Although it may appear there are a large number of types of articles published due to the wide variety of names they are published under, most articles published are one of the following types; Original Research, Review Articles, Short reports or Letters, Case Studies, Methodologies.

Original Research:

This is the most common type of journal manuscript used to publish full reports of data from research. It may be called an  Original Article, Research Article, Research, or just  Article, depending on the journal. The Original Research format is suitable for many different fields and different types of studies. It includes full Introduction, Methods, Results, and Discussion sections.

Short reports or Letters:

These papers communicate brief reports of data from original research that editors believe will be interesting to many researchers, and that will likely stimulate further research in the field. As they are relatively short the format is useful for scientists with results that are time sensitive (for example, those in highly competitive or quickly-changing disciplines). This format often has strict length limits, so some experimental details may not be published until the authors write a full Original Research manuscript. These papers are also sometimes called Brief communications .

Review Articles:

Review Articles provide a comprehensive summary of research on a certain topic, and a perspective on the state of the field and where it is heading. They are often written by leaders in a particular discipline after invitation from the editors of a journal. Reviews are often widely read (for example, by researchers looking for a full introduction to a field) and highly cited. Reviews commonly cite approximately 100 primary research articles.

TIP: If you would like to write a Review but have not been invited by a journal, be sure to check the journal website as some journals to not consider unsolicited Reviews. If the website does not mention whether Reviews are commissioned it is wise to send a pre-submission enquiry letter to the journal editor to propose your Review manuscript before you spend time writing it.  

Case Studies:

These articles report specific instances of interesting phenomena. A goal of Case Studies is to make other researchers aware of the possibility that a specific phenomenon might occur. This type of study is often used in medicine to report the occurrence of previously unknown or emerging pathologies.

Methodologies or Methods

These articles present a new experimental method, test or procedure. The method described may either be completely new, or may offer a better version of an existing method. The article should describe a demonstrable advance on what is currently available.

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• How to Write a Literature Review | Guide, Examples, & Templates

How to Write a Literature Review | Guide, Examples, & Templates

Published on January 2, 2023 by Shona McCombes . Revised on September 11, 2023.

What is a literature review? A literature review is a survey of scholarly sources on a specific topic. It provides an overview of current knowledge, allowing you to identify relevant theories, methods, and gaps in the existing research that you can later apply to your paper, thesis, or dissertation topic .

There are five key steps to writing a literature review:

• Search for relevant literature
• Evaluate sources
• Identify themes, debates, and gaps
• Outline the structure
• Write your literature review

A good literature review doesn’t just summarize sources—it analyzes, synthesizes , and critically evaluates to give a clear picture of the state of knowledge on the subject.

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Table of contents

What is the purpose of a literature review, examples of literature reviews, step 1 – search for relevant literature, step 2 – evaluate and select sources, step 3 – identify themes, debates, and gaps, step 4 – outline your literature review’s structure, step 5 – write your literature review, free lecture slides, other interesting articles, frequently asked questions, introduction.

• Quick Run-through
• Step 1 & 2

When you write a thesis , dissertation , or research paper , you will likely have to conduct a literature review to situate your research within existing knowledge. The literature review gives you a chance to:

• Demonstrate your familiarity with the topic and its scholarly context
• Develop a theoretical framework and methodology for your research
• Position your work in relation to other researchers and theorists
• Show how your research addresses a gap or contributes to a debate
• Evaluate the current state of research and demonstrate your knowledge of the scholarly debates around your topic.

Writing literature reviews is a particularly important skill if you want to apply for graduate school or pursue a career in research. We’ve written a step-by-step guide that you can follow below.

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Writing literature reviews can be quite challenging! A good starting point could be to look at some examples, depending on what kind of literature review you’d like to write.

• Example literature review #1: “Why Do People Migrate? A Review of the Theoretical Literature” ( Theoretical literature review about the development of economic migration theory from the 1950s to today.)
• Example literature review #2: “Literature review as a research methodology: An overview and guidelines” ( Methodological literature review about interdisciplinary knowledge acquisition and production.)
• Example literature review #3: “The Use of Technology in English Language Learning: A Literature Review” ( Thematic literature review about the effects of technology on language acquisition.)
• Example literature review #4: “Learners’ Listening Comprehension Difficulties in English Language Learning: A Literature Review” ( Chronological literature review about how the concept of listening skills has changed over time.)

You can also check out our templates with literature review examples and sample outlines at the links below.

Download Word doc Download Google doc

Before you begin searching for literature, you need a clearly defined topic .

If you are writing the literature review section of a dissertation or research paper, you will search for literature related to your research problem and questions .

Make a list of keywords

Start by creating a list of keywords related to your research question. Include each of the key concepts or variables you’re interested in, and list any synonyms and related terms. You can add to this list as you discover new keywords in the process of your literature search.

• Social media, Facebook, Instagram, Twitter, Snapchat, TikTok
• Body image, self-perception, self-esteem, mental health
• Generation Z, teenagers, adolescents, youth

Search for relevant sources

Use your keywords to begin searching for sources. Some useful databases to search for journals and articles include:

• Your university’s library catalogue
• Google Scholar
• Project Muse (humanities and social sciences)
• Medline (life sciences and biomedicine)
• EconLit (economics)
• Inspec (physics, engineering and computer science)

You can also use boolean operators to help narrow down your search.

Make sure to read the abstract to find out whether an article is relevant to your question. When you find a useful book or article, you can check the bibliography to find other relevant sources.

You likely won’t be able to read absolutely everything that has been written on your topic, so it will be necessary to evaluate which sources are most relevant to your research question.

For each publication, ask yourself:

• What question or problem is the author addressing?
• What are the key concepts and how are they defined?
• What are the key theories, models, and methods?
• Does the research use established frameworks or take an innovative approach?
• What are the results and conclusions of the study?
• How does the publication relate to other literature in the field? Does it confirm, add to, or challenge established knowledge?
• What are the strengths and weaknesses of the research?

Make sure the sources you use are credible , and make sure you read any landmark studies and major theories in your field of research.

You can use our template to summarize and evaluate sources you’re thinking about using. Click on either button below to download.

Take notes and cite your sources

As you read, you should also begin the writing process. Take notes that you can later incorporate into the text of your literature review.

It is important to keep track of your sources with citations to avoid plagiarism . It can be helpful to make an annotated bibliography , where you compile full citation information and write a paragraph of summary and analysis for each source. This helps you remember what you read and saves time later in the process.

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To begin organizing your literature review’s argument and structure, be sure you understand the connections and relationships between the sources you’ve read. Based on your reading and notes, you can look for:

• Trends and patterns (in theory, method or results): do certain approaches become more or less popular over time?
• Themes: what questions or concepts recur across the literature?
• Debates, conflicts and contradictions: where do sources disagree?
• Pivotal publications: are there any influential theories or studies that changed the direction of the field?
• Gaps: what is missing from the literature? Are there weaknesses that need to be addressed?

This step will help you work out the structure of your literature review and (if applicable) show how your own research will contribute to existing knowledge.

• Most research has focused on young women.
• There is an increasing interest in the visual aspects of social media.
• But there is still a lack of robust research on highly visual platforms like Instagram and Snapchat—this is a gap that you could address in your own research.

There are various approaches to organizing the body of a literature review. Depending on the length of your literature review, you can combine several of these strategies (for example, your overall structure might be thematic, but each theme is discussed chronologically).

Chronological

The simplest approach is to trace the development of the topic over time. However, if you choose this strategy, be careful to avoid simply listing and summarizing sources in order.

Try to analyze patterns, turning points and key debates that have shaped the direction of the field. Give your interpretation of how and why certain developments occurred.

If you have found some recurring central themes, you can organize your literature review into subsections that address different aspects of the topic.

For example, if you are reviewing literature about inequalities in migrant health outcomes, key themes might include healthcare policy, language barriers, cultural attitudes, legal status, and economic access.

Methodological

If you draw your sources from different disciplines or fields that use a variety of research methods , you might want to compare the results and conclusions that emerge from different approaches. For example:

• Look at what results have emerged in qualitative versus quantitative research
• Discuss how the topic has been approached by empirical versus theoretical scholarship
• Divide the literature into sociological, historical, and cultural sources

Theoretical

A literature review is often the foundation for a theoretical framework . You can use it to discuss various theories, models, and definitions of key concepts.

You might argue for the relevance of a specific theoretical approach, or combine various theoretical concepts to create a framework for your research.

Like any other academic text , your literature review should have an introduction , a main body, and a conclusion . What you include in each depends on the objective of your literature review.

The introduction should clearly establish the focus and purpose of the literature review.

Depending on the length of your literature review, you might want to divide the body into subsections. You can use a subheading for each theme, time period, or methodological approach.

As you write, you can follow these tips:

• Summarize and synthesize: give an overview of the main points of each source and combine them into a coherent whole
• Analyze and interpret: don’t just paraphrase other researchers — add your own interpretations where possible, discussing the significance of findings in relation to the literature as a whole
• Critically evaluate: mention the strengths and weaknesses of your sources
• Write in well-structured paragraphs: use transition words and topic sentences to draw connections, comparisons and contrasts

In the conclusion, you should summarize the key findings you have taken from the literature and emphasize their significance.

When you’ve finished writing and revising your literature review, don’t forget to proofread thoroughly before submitting. Not a language expert? Check out Scribbr’s professional proofreading services !

This article has been adapted into lecture slides that you can use to teach your students about writing a literature review.

Scribbr slides are free to use, customize, and distribute for educational purposes.

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If you want to know more about the research process , methodology , research bias , or statistics , make sure to check out some of our other articles with explanations and examples.

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A literature review is a survey of scholarly sources (such as books, journal articles, and theses) related to a specific topic or research question .

It is often written as part of a thesis, dissertation , or research paper , in order to situate your work in relation to existing knowledge.

There are several reasons to conduct a literature review at the beginning of a research project:

• To familiarize yourself with the current state of knowledge on your topic
• To ensure that you’re not just repeating what others have already done
• To identify gaps in knowledge and unresolved problems that your research can address
• To develop your theoretical framework and methodology
• To provide an overview of the key findings and debates on the topic

Writing the literature review shows your reader how your work relates to existing research and what new insights it will contribute.

The literature review usually comes near the beginning of your thesis or dissertation . After the introduction , it grounds your research in a scholarly field and leads directly to your theoretical framework or methodology .

A literature review is a survey of credible sources on a topic, often used in dissertations , theses, and research papers . Literature reviews give an overview of knowledge on a subject, helping you identify relevant theories and methods, as well as gaps in existing research. Literature reviews are set up similarly to other  academic texts , with an introduction , a main body, and a conclusion .

An  annotated bibliography is a list of  source references that has a short description (called an annotation ) for each of the sources. It is often assigned as part of the research process for a  paper .  

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Research Paper Vs Review Paper | 50 Differences

50 Differences Between Research Article and a Review Article

Table of contents

A research paper is a piece of writing that reports facts, data, and other information on a specific topic. It is usually longer than a review paper and includes a detailed evaluation of the research. Whereas, a review paper is a shorter piece of writing that summarizes and evaluates the research on a specific topic. It is usually shorter than a research paper and does not include a detailed evaluation of the research. In this article, we have listed the 50 important differences between a review paper vs research article.

• A research paper is typically much longer than a review paper.
• A research paper is typically more detailed and comprehensive than a review paper.
• A research paper is typically more focused on a specific topic than a review paper.
• A research paper is typically more analytical and critical than a review paper.
• A research paper is typically more objective than a review paper.
• A research paper is typically written by one or more authors, while a review paper may be written by a single author.
• A research paper is typically peer-reviewed, while a review paper may not be.
• A research paper is typically published in a scholarly journal, while a review paper may be published in a variety of different publications.
• The audience for a research paper is typically other scholars, while the audience for a review paper may be the general public.
• The purpose of a research paper is typically to contribute to the scholarly literature, while the purpose of a review paper may be to provide an overview of the literature or to evaluate a particular research study.
• The structure of a research paper is typically more complex than the structure of a review paper.
• A research paper typically includes an abstract, while a review paper may not.
• A research paper typically includes a literature review, while a review paper may not.
• A research paper typically includes a methodology section, while a review paper may not.
• A research paper typically includes results and discussion sections, while a review paper may not.
• A research paper typically includes a conclusion, while a review paper may not.
• A research paper is typically organized around a central research question , while a review paper may be organized around a central theme.
• A research paper typically uses primary sources, while a review paper may use both primary and secondary sources.
• A research paper is typically based on empirical research, while a review paper may be based on either empirical or non-empirical research.
• A research paper is typically more formal than a review paper.
• A research paper is typically written in the third person, while a review paper may be written in the first person.
• A research paper typically uses formal language, while a review paper may use more informal language.
• A research paper is typically objective in tone, while a review paper may be more subjective in tone.
• A research paper typically uses APA style, while a review paper may use a different style.
• A research paper typically includes a title page, while a review paper may not.
• A research paper typically includes an abstract on the title page, while a review paper may not.
• A research paper typically includes keywords on the title page, while a review paper may not.
• A research paper typically includes an author note, while a review paper may not.
• A research paper is typically organized around a central research question, while a review paper may be organized around a central theme.
• A research paper is typically longer than a review paper.

I hope, this article would help you to know the differences between Research Paper and a Review Paper.

Also Read: What is a Research Design? Importance and Types

• Difference between
• evaluation review paper
• Research Paper

What is a Research Design? Importance and Types

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Review Typologies

There are many types of evidence synthesis projects, including systematic reviews as well as others. The selection of review type is wholly dependent on the research question. Not all research questions are well-suited for systematic reviews.

• Review Typologies (from LITR-EX) This site explores different review methodologies such as, systematic, scoping, realist, narrative, state of the art, meta-ethnography, critical, and integrative reviews. The LITR-EX site has a health professions education focus, but the advice and information is widely applicable.

Review the table to peruse review types and associated methodologies. Librarians can also help your team determine which review type might be appropriate for your project. 

Reproduced from Grant, M. J. and Booth, A. (2009), A typology of reviews: an analysis of 14 review types and associated methodologies. Health Information & Libraries Journal, 26: 91-108.  doi:10.1111/j.1471-1842.2009.00848.x

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Difference between Research Paper and Review Paper

Scholarly literature can be of different types. Many of them require researchers to perform an original study, whereas others are based on previously published research. Amateur researchers have quite a confusion understanding each type of scholarly literature and the difference between them.

Research Paper

When researchers partake in an original study or investigation of a unique topic, for example, a study of the prevalence of substance abuse in a specific community or geographical area, the findings of that study are presented as a research paper. The most essential component of a research paper is the analysis of the topic, evidence to support the study and the conclusion of the study. It can comprise of the answer to the reach question and may include a hypothesis, the resource requirement for the study and the method followed to reach the conclusion. The formatting of a research paper is fairly similar across all subjects and institutions, though it can vary from one region to another depending upon the pattern laid down by the publishing and educational bodies. This scholarly work is unique and bears no similarity to any other published work. Analysis of the data can vary from the use of software to authentic experiments.

Review Paper

Review papers are universal and can be focused upon a wide range of mediums, including articles in journals, books, magazines, and software. A review paper refers to the study and survey of a recently published Research paper on a specific topic or subject. For instance, climate change due to industrial waste has many scholarly Research paper. these papers can be reviewed by any other number of scholars for its merits. In order to write a review paper successfully, one needs to have knowledge of what other scholars have written on the subject and their thoughts on the subject, particularly in recent times. the reach papers act as a reference and source material for these review papers. These can be stimulating and extremely exhaustive with the intent for undertaking research by introducing challenging materials and facts. It should act as a summary of the original research paper with all its relevant literature on the topic.

Key differences between the Research paper and Review paper are given in the table below:

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Types of Research Papers: Overview

A research paper is simply a piece of writing that uses outside sources. There are different types of research papers with varying purposes and expectations for sourcing.

While this guide explains those differences broadly, disciplines and assignments vary. Ask your professor for clarification on the purpose and types of appropriate research questions and sources.

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• Open access
• Published: 29 March 2023

Mapping ethical issues in the use of smart home health technologies to care for older persons: a systematic review

• Nadine Andrea Felber   ORCID: orcid.org/0000-0001-8207-2996 1 ,
• Yi Jiao (Angelina) Tian   ORCID: orcid.org/0000-0003-2969-9655 1 ,
• Félix Pageau   ORCID: orcid.org/0000-0002-4249-7399 2 ,
• Bernice Simone Elger   ORCID: orcid.org/0000-0003-0857-0510 1 &
• Tenzin Wangmo 1  

BMC Medical Ethics volume  24 , Article number:  24 ( 2023 ) Cite this article

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The worldwide increase in older persons demands technological solutions to combat the shortage of caregiving and to enable aging in place. Smart home health technologies (SHHTs) are promoted and implemented as a possible solution from an economic and practical perspective. However, ethical considerations are equally important and need to be investigated.

We conducted a systematic review according to the PRISMA guidelines to investigate if and how ethical questions are discussed in the field of SHHTs in caregiving for older persons.

156 peer-reviewed articles published in English, German and French were retrieved and analyzed across 10 electronic databases. Using narrative analysis, 7 ethical categories were mapped: privacy, autonomy, responsibility, human vs. artificial interactions, trust, ageism and stigma, and other concerns.

The findings of our systematic review show the (lack of) ethical consideration when it comes to the development and implementation of SHHTs for older persons. Our analysis is useful to promote careful ethical consideration when carrying out technology development, research and deployment to care for older persons.

Registration

We registered our systematic review in the PROSPERO network under CRD42021248543.

Peer Review reports

Introduction/background

Significant advancements in medicine, public health and technology are allowing the world population to grow increasingly older adding to the steady rise in the proportion of senior citizens (aged over 65) [ 1 ]. Because of this growth in the aging population, the demand for and financial costs of caring for older adults are both rising [ 2 ]. That older persons generally wish to age in place and receive healthcare at home [ 2 ] may mean accepting risks such as falling, a risk that increases with frailty [ 3 ]. However, many prefer accepting these risks rather than moving into long term care facilities [ 4 , 5 , 6 ].

A solution to this multi-facetted problem of ageing safely at home and receiving appropriate care, while keeping costs at bay may be the use of smart home health technologies (SHHTs). A smart home is defined by Demiris and colleagues as “ residence wired with technology features that monitor the well-being and activities of their residents to improve overall quality of life, increase independence and prevent emergencies” [ 7 ]. SHHTs then, represent a certain type of smart home technology, which include non-invasive, unobtrusive, interoperable and possibly wearable technologies that use a concept called the Internet-of-Things (IoT) [ 8 ]. These technologies could thereby remotely monitor the older resident and register any abnormal deviations in the daily habits and vital signs while sending alerts to their formal and informal caregivers when necessary. These SHHTs could permit older people (and their caregivers) to receive the necessary medical support and attention at their convenience and will, thereby allowing them to continue living independently in their home environment.

All of these functions offer benefits to older persons wishing to age at home. While focusing on practical advantages is important, an equally important question to ask is how ethical these technologies are when used in the care of older persons. Principles of biomedical ethics, such as autonomy, justice [ 9 ], privacy [ 10 ], and responsibility [ 11 ] should not only be respected by medical professionals, but by technology developers and build-into the technologies as well.

The goal of our systematic review is therefore to investigate whether and which ethical concerns are discussed in the pertinent theoretical and empirical research on SHHTs for older persons between 2000 and 2020. Different from previous literature reviews [ 12 , 13 , 14 ],, which only explored practical aspects, we explicitly examined if and how researchers treated the ethical aspects of SHHTs in their studies, adding an important, yet often overlooked aspect to the systematic literature. Moreover, we present how and which ethical concerns are discussed in the theoretical literature and which ones in empirical literature, to shed light on possible gaps regarding which and how different ethical concerns are developed. Identifying these gaps is the first important step to eventually connecting bioethical considerations to the real world, adapting policies, guidelines and technologies itself [ 15 ]. Thus, our systematic review is the first one to do so in the context of ethical issues in SHHTs used for caregiving for older persons.

Search strategy

With the guidance of an information specialist from the University of Basel, our team developed a search strategy according to the PICO principle: Population 1 (Older adults), Population 2 (Caregivers), Intervention (Smart home health technologies), and Context (Home). The outcome of ethics was intentionally omitted as we wanted to capture all relevant studies without narrowing concerns that we would classify as “ethical”. Within each category, synonyms and spelling variations for the keywords were used to include all relevant studies. We then adapted the search string by using database-specific thesaurus terms in all ten searched electronic databases: EMBASE, Medline, PsycINFO, CINAHL, SocIndex, SCOPUS, IEEE, Web of Science, Philpapers, and Philosophers Index. We limited the search to peer-reviewed papers published between January 1st, 2000 and December 31st, 2020, written in the English, French, and German languages. This time frame allowed us to map the evolution to SHHTs as a new field.

The inclusion criteria were the following: (1) The article must be an empirical or theoretical original research contribution. Hence, book chapters, conference proceedings, newspaper articles, commentary, dissertations, and thesis were excluded. Also excluded were other systematic reviews since their inclusion would duplicate findings from our individual studies. (2) When the included study was empirical, the study’s population of interest must be older persons over 65 years of age, and/or professional or informal caregivers who provide care to older persons. Informal caregivers include anyone in the community who provided support without financial compensation. Professional caregivers include nurses and related professions who receive financial compensation for their caregiving services. (3) The included study must investigate SHHTs and their use in the older persons’ place of dwelling.

First, we carried out the systematic search across databases and removed all duplicates through EndNote (see supplementary Table  1 in appendix part 1 for a list of all included articles). One member of the research team screened all titles manually and excluded irrelevant papers. Then, two authors screened the abstracts and excluded irrelevant papers, and any disagreements were solved by a third author. She then also combined all included articles and removed further duplicates.

PRISMA 2020 Flowchart

Final inclusion and data extraction

All included articles were searched and retrieved online (and excluded if full text was not available). Three co-authors then started data extraction, where several papers were excluded due to irrelevant content. To code the extracted data, a template was developed, which was tested in a first round of data extraction and then used in Microsoft Excel during the remaining extraction process. Study demographics and ethical considerations were recorded. Each extracting author was responsible for a portion of articles. If uncertainties or disputes occurred, they were solved by discussion. To ensure that our data extraction was not biased, 10% of the articles were reviewed independently. Upon comparing data extracted of those 10% of our overall sample, we found that items extracted reached 80% consistency.

Data synthesis

The extracted datasets were combined and ethical discussions encountered in the publications were analyzed using narrative synthesis [ 16 ]. During this stage, the authors discussed the data and recognized seven first-order ethical categories. Information within these categories were further analyzed to form sub-categories that describe and/or add further information to the key ethical category.

Nature of included articles

Our search initially identified 10,924 papers in ten databases. After the duplicates were removed, 9067 papers remained whose titles were screened resulting in exclusion of 5215 papers (Fig.  1 ). The examination of remaining 3845 abstracts of articles led to the inclusion of 374 papers for full-texts for retrieval. As we were unable to find 20 papers after several attempts, the remaining 354 full-texts were included for full-text review. In this full-text review phase, we further excluded 198 full-texts with reasons (such as technologies employed in hospitals, or technologies unrelated to health). Ultimately, this systematic review included 144 empirical and 12 theoretical papers specifying normative considerations of SHHTs in the context of caregiving for older persons.

Almost all publications (154 out of 156) were written in English, and over 67% [ 105 ] were published between 2014 and 2020. About a quarter (26%; 41 papers) were published between 2007 and 2013 and only 7% (10 articles) were from 2000 to 2006. Apart from the 12 theoretical papers, the methodology used in the 144 empirical papers included the following: 42 articles (29%) used a mixed-methods approach, 39 (27%) experimental, 38 (26%) qualitative, 15 (10%) quantitative, and the remaining were of an observational, ethnographical, case-study, or iterative testing nature.

The functions of SHHTs tested or studied in the included empirical papers were categorized as such: 29 articles (20.14%) were solely involved with (a) physiological and functioning monitoring technologies, 16 (11.11%) solely with (b) safety/security monitoring and assistance functions, 23 (15.97%) solely promoted (c) social interactions, and 9 (6.25%) solely for (d) cognitive and sensory assistance. However, 46 articles (29%) also involved technologies that fulfilled more than one of the categorized functions. The specific types of SHHTs included in this review comprised: intelligent homes (71 articles, 49.3%); assistive autonomous robots (49 articles, 34.03%); virtual/augmented/mixed reality (7, 4.4%); and AI-enabled health smart apps and wearables (4 articles, 1.39%). Likewise, the remaining 20 articles (12.8.8%) involved either multiple technologies or those that did not fall into any of the above categories.

Ethical considerations

Of the 156 papers included, 55 did not mention any ethical considerations (See supplementary Table  1 in appendix part 1). Among the 101 papers that noted one or more ethical considerations, we grouped them into 7 main categories (1) privacy, (2) human vs. artificial relationships, (3) autonomy, (4) responsibility, (5) social stigma and ageism, (6) trust, and (7) other normative issues (see Table  1 ). Each of these categories consists of various sub-categories that provided more information on how smart home health technologies (possibly) affected or interacted with the older persons or caregivers in the context of caregiving (Table  2 ). Each of the seven ethical considerations are explained in depth in the following paragraphs.

This key category was cited across 58 articles. In theoretical articles, privacy was one of the most often discussed ethical consideration, as 9 out of 12 mentioned privacy related concerns. Among the 58 articles, four sub-issues within privacy were discussed.

(A)The awareness of privacy was reported as varying according to the type of SHHT end-user. Whereas some end-users were more aware or privacy in relation to SHHTs, others denoted little or a total lack of consideration, while some had differing levels of concerns for privacy that changed as it is weighed against other values, such as access to healthcare [ 17 ] or feeling of safety [ 18 ]. Both caregivers and researchers often took privacy concerns into account [ 19 , 20 , 21 ], while older persons themselves did not share the same degree of fears or concerns [ 22 , 23 , 24 ]. Older persons in fact were less concerned about privacy than costs and usability [ 23 ]. Furthermore, they were willing to trade privacy for safety and the ability to live at home. Nevertheless, several papers acknowledged that privacy is an individualized value, whereby its significance depends on both the person and their context, thus their preferences cannot be generalized [ 25 , 26 , 27 , 28 ]. Lastly, there were also some papers that explicitly stated that there were no privacy concerns found by the participants, or that participants found it useful to have monitoring without mentioning privacy as a barrier [ 29 , 30 , 31 ].

The second prevalent sub-issue within privacy was (B) privacy by choice. Both older persons and their caregivers expressed a preference for having a choice in technology used, in what data is collected, and where technology should or should not be to installed [ 32 , 33 ]. For example, some spaces were perceived as more private and thus monitoring felt more intrusive [ 34 , 35 , 36 ]. Formal caregivers were concerned about monitoring technologies being used as a recording device for their work [ 37 , 38 ]. Furthermore, older persons were often worried about cameras [ 39 , 40 ] and “eyes watching”, even if no cameras were involved [ 41 , 42 , 43 ].

The third privacy concern was (C) risk and regulation of privacy, which included discussions surrounding dissemination of data or active data theft [ 44 , 45 , 46 , 47 ], as well as change in behavior or relationships due to interaction with technology [ 48 , 49 ]. Researchers were aware of both legal and design-contextual measures that must be observed in order to ensure that these risks were minimized [ 45 , 50 , 51 ].

The final sub-issue that we categorized was (D) privacy in the case of cognitive impairment. This included disagreements if cognitive impairment warrants more intrusive measures or if privacy should be protected for everyone in the same way [ 52 , 53 ].

Human versus artificial relationships

54 articles in our review contained data pertinent to trade-offs between human and artificial caregiving. Firstly, (A) there was a general fear that robots would replace humans in providing care for older persons [ 28 , 54 , 55 , 56 ], along with related concerns such as losing jobs [ 40 , 57 ], disadvantages with substituting real interpersonal contact [ 17 , 46 ], and thus increasing the negative effects associated with social isolation [ 41 , 58 ].

Many papers also emphasized (B) the importance of human caregiving, underlining the necessity of human touch [ 26 , 47 , 50 , 59 ] believing that technology should and could not replace humans in connections [ 17 ], love [ 33 ], relationships [ 60 ], and care through attention to subtle signs of health decline in every in-person visit [ 57 ]. Older persons also preferred human contact over machines and had guarded reactions to purely virtual relationships[ 31 , 61 , 62 ]. The use of technology was seen to dehumanize care, as care should be inherently human-oriented [ 27 , 48 ].

There was data alluding to (C) the positive reactions to technologies performing caregiving tasks and possibly forming attachments with the technology[ 47 , 49 , 58 ]. Furthermore, some papers cited participants reacting positively to robots replacing human care, where the concept of “good care” could be redefined [ 63 , 64 , 65 , 66 ]. Solely theoretical papers also identified possible benefits of tech for socialization and relationship building [ 67 , 68 ].

Finally, many articles raised the idea of (D) collaboration between machine and human to provide caregiving to older persons [ 69 ]. These studies highlighted the possible harms if such collaboration was not achieved, such as informal caregivers withdrawing from care responsibilities [ 70 ] or the reinforcement of oppressive care relations [ 71 ]. Interestingly, opinions varied on whether the caregiving technology, such as a robot should have “life-like” appearance, voices, and emotional expressions, while recognizing the current technological limits in actually providing those features to a satisfactory level [ 46 ]. For example, some users preferred for the robot to communicate with voice commands, while others wanted to further customize this function with specific requests on the types of voices generated [ 65 , 72 ].

40 papers mentioned autonomy of the older person with respect to the use of SHHTs. The first sub-theme categorized was in relation to (A) control, which encompassed positive aspects like (possible) empowerment through technology [ 25 , 26 , 73 , 74 ] and negative aspects such as the possibility of technology taking control over the older person, thus increasing dependence [ 55 , 75 ] or decreasing freedom of decision making [ 48 ]. Several studies reported the wishes of older persons to be in control when using the technology (e.g. technology should be easily switched off or on) and be in control of its potential, meaning the extend of data collected or transferred, for example [ 17 , 30 , 70 , 76 ]. Furthermore, they should have the option to not use technology in spaces where they do not wish to, e.g., public spaces [ 35 ]. The issue of increased dependency was discussed as a loss or rather, fear of the loss of autonomy due to greater reliance on technology as well as the fear of being monitored all the time [ 28 , 48 ]. In addition, using technology was deemed to make older persons more dependent and to increase isolation [ 77 ].

The second sub-category within autonomy highlighted the need for the technology to (B) protect the autonomy and dignity of its older end-users, which also included the unethical practice of deception (e.g.[ 46 , 49 , 54 , 78 ], infantilization [ 31 , 60 ], or paternalism [ 17 , 27 , 57 ], as a way to disrespect older persons’ dignity and autonomy [ 79 , 80 , 81 ]. Also reported was that these users may accept technology to avoid being a burden on others, thus underscoring the value of technology to enhance functional autonomy, understood here as independent functioning [ 52 , 82 , 83 ]. Other studies mentioned this kind of trade-off between autonomy and other values or interests as well. For example, between respecting the autonomy of the older persons versus nudging them towards certain behavior (perceived as beneficial for them) through the help of technology [ 32 ], or between autonomy and safety [ 24 ].

Two sub-issues within autonomy primarily discussed in the theoretical publications were (C) relational autonomy [ 27 , 41 , 49 , 58 ] and (D) explanations on why autonomy should actually be preserved. The former emphasized the fact that older persons do not and should not live isolated lives and that there should be respect and promotion of their relationships with family members, friends, caregivers, and the community as a whole [ 27 , 47 ]. The latter described the benefits of respecting autonomy, such as increased happiness and well-being [ 65 , 67 ] or a sense of purpose [ 84 ], and thus favoring the promotion of autonomy and choice also from a normative perspective.

Responsibility

This theme included data across 25 articles that mentioned concerns such as the effect of using technologies on the current responsibilities of caregivers and older persons themselves. Specifically, the papers discussed (A) the downsides of assistive home technology on responsibility. That is, the use of technology conflicted with moral ideas around responsibility [ 58 ], especially for caregivers [ 57 , 59 ]. Its use also raised more practical concerns, such as the fear of shifting the responsibility onto the technology and thus, diminishing vigilance and/or care. Related to this thought was also a fear of increased responsibility on both older persons [ 60 ] and their caregivers, who were worried about extra work time was needed to integrate technology into their work, learn its functions, analyze data, and respond to potentially higher frequencies of alerts [ 18 , 35 , 36 , 53 , 85 ].

Additionally, studies reported (B) continuous negotiation between (formal) caregivers’ (professional) responsibilities of care and the opportunities that smart technologies could provide [ 26 , 47 , 55 , 70 , 82 ]. For example, increased need for cooperation between informal and formal caregivers due to technology was foreseen [ 81 ] and fear expressed that over-reliance on female caregivers was exacerbated [ 71 ]. Nevertheless, the use of smart home health technologies was often seen to (C) reduce the burden of care, where caregivers could direct their attention and time to the most-needed situations and better align the responsibilities of care [ 5 , 18 , 49 , 74 , 80 , 81 ]. This shift of burden onto a technology was also reported by older persons as freeing [ 48 ].

Ageism and stigma

24 articles discussed ageism and stigma, which included discussions about fear of (A) being stigmatized by others with the use of SHHTs [ 73 , 86 ]. Older persons thought acceptance of such technologies also alluded to an admission of failure [ 82 ], or being perceived by others as frail, old, forgetful [ 77 , 87 ], or even stupid [ 26 , 33 , 88 ]. This resulted in them expressing ageist views stating that they did not need the technology “yet” [ 84 , 89 ]. Some papers reported the belief that the presence of robots was disrespectful for older people [ 52 , 85 , 90 ] and technologies do little to alleviate frustration and the impression of “being stupid” that older persons may have when they are faced with the complexities of the healthcare system [ 73 ]. Furthermore, older persons in a few studies did express unfamiliarity with learning new technologies in old age [ 42 , 66 , 91 ], coupled with fears of falling behind and not keeping up with their development, and feeling pressured to use technology [ 62 , 89 ].

Within ageism and stigma, (B) social influence was deemed to cause older persons to believe that the longer they have been using technology, the more their loved ones want them to use it as well, creating a sort of reinforcing loop [ 27 ]. Other social points were related to self-esteem, meaning that older persons needed to reach a certain threshold first to publicly admit that they need technology [ 85 ], or doubts by caregivers if they were able to use the devices [ 36 ]. This possibly led older persons to prefer unobtrusive technology and those that could not be noticed by visitors [ 22 , 55 , 88 ].

Lastly, (C) two theoretical articles raised concerns in regard to technology exacerbating stigmatization of women and migrants in caregiving. Both Parks [ 47 ] and Roberts & Mort [ 71 ] suggested that caregiving technology which does not question the underlying expectation that women give care to their relatives will worsen such gendered expectations in caregiving.

We identified 18 articles that mentioned some aspect of trust. For both older persons and caregivers, there was often (A) a general mistrust with technologies compared with existing human caregiving [ 33 , 42 ]. Therefore, caregivers became proxies and were relied on to “understand it” and continue providing care [ 48 ]. For caregivers the lack of trust was associated with the use of technologies, for example, leaving older persons alone with technology [ 81 ], worrying that older persons would not trust the technology [ 29 , 32 ] or that it could change their professional role [ 23 ]. One paper even reported that using technology meant caregivers themselves are not trusted [ 92 ]. Surprisingly, some studies found that older persons had no problem trusting technology, even considering it safer and more reliable than humans [ 58 , 70 ].

The second sub-theme concerned (B) characteristics promoting trust. That is, the degree of automation [ 30 ](, the involvement of trusted humans in design and use [ 34 , 93 ], perceived usefulness of the technology and spent time with the technology all influenced trust [ 59 , 72 , 94 ]. For robots specifically, they were trusted more than virtual agents, such as Alexa [ 60 , 65 ]. Taking this step further, studies discovered that robots with a higher degree of automation or a lower degree in anthropomorphism level increased trust [ 30 ].

There were several miscellaneous considerations not fitting the ones already mentioned above, and we categorized them as follows. Firstly, two theoretical articles mentioned (A) considerations related to research. Ho, [ 27 ] pointed out that empirical evidence of the usefulness of SHHTs is lacking, which therefore may make them less relevant as a possible solution for aging in place. Palm et al. (2013) suggested that, if research would consider the fact that many costs of caregiving are hidden because of non-paid informal caregivers, the actual economic benefits of SHHTs are unknown. Lastly, two articles alluded to (B) psychological phenomena related to the use of SHHTs. Pirhonen et al., [ 58 ] suggested that robots can promote the ethical value of well-being through the promotion of feelings of hope. The other phenomenon was feeling of blame and fear associated with the adoption of the technology, as caregivers may be pushed to use SHHTs in order to not be blamed for failing to use technology [ 18 ]. This then also nudged caregivers to think that using SHHTs cannot do any harm, so it is better to use it than not use it.

Our systematic review investigated if and how ethical considerations appear in the current research on SHHTs in the context of caregiving for older persons. As we included both empirical and theoretical works of literature, our review is more comprehensive that existing systematic reviews (e.g.[ 12 , 13 , 14 ], that have either only explored the empirical side of the research and neglected to study ethical concerns. Our review offers an informative and useful insights on dominant ethical issues related to caregiving, such as autonomy and trust [ 95 , 96 ]. At the same time, the study findings brings forth less known ethical concerns that arise when using technologies in the caregiving context, such as responsibility [ 97 ] and ageism and stigma.

The first key finding of our systematic review is the silence on ethics in SHHTs research for caregiving purposes. Over a third of the reviewed publications did not mention any ethical concern. One possible explanation is related to scarcity [ 98 ]. In the context of research in caregiving for older persons, “scarcity” can be understood in a variety of ways: one way is to see the available space for ethical principles in medical technology research as scarce. For example, according to Einav & Ranzani [ 99 ] “Medical technology itself is not required to be ethical; the ethics of medical technology revolves around when, how and on whom each technology is used” (p.1612). Determining the answers to these questions is done empirically, by providing proof of benefit of the technology, ongoing reporting on (possibly harmful) long term effects, and so on [ 99 ]. Given that publication space in journal is limited to a certain amount of text, the available space that ethical considerations can take up is scarce. Therefore, adding deliberations about the unearthed values or issues in our systematic review, like trust, responsibility or ageism, may simply not fit in the space available in research publications. This may also be the reason why the values of beneficence and non-maleficence were not found through our narrative analysis. While both values are considered crucial in biomedical ethics [ 9 ], the empirically measured benefits may be considered enough by the authors to demonstrate beneficence (and non-maleficence), leading them to not mention the ethical values explicitly again in their publications.

Another interpretation is the scarcity of time, and the felt pressure to “solve” the problem of limited resources in caregiving [ 2 ]. Researchers might be therefore more inclined to focus on the empirical data showing benefits, rather than to engage in elaborations on ethical issues that arise with those benefits. Lastly, as researchers have to compete for limited funding [ 100 ] and given that technological research receives more funding than biomedical ethics [ 101 ], it is likely that the numbers of publications mentioning purely empirical studies exceeds those publications that solely mention the ethical issues (as our theoretical papers did) or that combine empirical and ethical parts. Further research needs to investigate these hypotheses further.

It is not surprising that privacy was the most discussed ethical issue in relation to SHHTs in caregiving. The topic of privacy, especially in relation to monitoring technologies and/or health, has been widely discussed (see for example [ 102 , 103 , 104 ]. A particularly interesting finding within this ethical concern was related to privacy and cognitive impairment. While discussions around autonomy and cognitive impairment are popular in bioethical research (see e.g. [ 105 , 106 ], privacy, on the other hand, has recently gained more attention for both researchers and designers [ 107 ]. The relation in the reviewed studies between cognitive impairment and privacy seemed to be reversely correlated –intrusions into the privacy of older persons with cognitive impairments were deemed as more justified [ 35 , 53 ], which necessarily does not mean that its ethical, but a practical fact that such intrusions become possible or necessary in the given context. A possible explanation lies in the connectedness of autonomy and privacy, in the sense that autonomy is needed to consent for any sort of intrusions [ 108 ].

Surprisingly, more research papers mentioned the topic of human vs. artificial relationships as an ethical concern than autonomy. Autonomy is often the most discussed ethics topic when it comes to use of technology [ 96 ]. However, fears associated with technology replacing human care has recently gained traction [ 109 , 110 , 111 ].The significance of this theme is likely due to the fact that caregiving for older persons has been (and is) a very human-centric activity [ 112 ]. As mentioned before, the persons willing and able to do this labor (both paid and unpaid caregiver) are limited and their pool is shrinking [ 113 ]. The idea of technology possibly filling this gap is not new [ 114 ], but is also clearly causing wariness among both older persons and caregivers, as we have discovered [ 56 , 61 ]. Frequently mentioned was the fear of care being replaced by technology. This finding was to be expected, as nursing is not the only profession where introduction of technology caused fears of job loss [ 115 ]. Within this ethical concern, the importance of human touch and human interaction was underlined [ 110 , 111 ]. Human touch is an important asset for caregivers when they care for older patients, particularly those with dementia, as it is one of the few ways to establish connection and to calm the patient with dementia [ 116 ]. Similarly, human touch and face-to-face interactions are mentioned as a critical aspect of caregiving in general, both for the care recipient and the caregiver [ 117 , 118 ]. While caregivers see the aspect of touching and interacting with older care recipients as a way to make their actions more meaningful and healing [ 90 , 117 ], for care recipients being touched, talked and listened to is part of feeling respected and experiencing dignity [ 118 , 119 ]. Introducing technology into the caregiving profession may therefore quickly elicit associations with cold and lifeless objects [ 59 ]. Future developments, both in the design of the technologies themselves and their implementation in caregiving will require critical discussion among concerned stakeholders and careful decision on how and to what extent the human touch and human care must be preserved.

A unique ethical concern that we have not seen in previous research [ 120 , 121 ] is responsibility, and remarkable within this concern was SHHTs’ negative impact on it. As previously mentioned, the human being and human interaction are seen as central to caregiving [ 117 , 118 ]. This can possibly be extended to concepts exclusively attributable to humans, such as the concept of moral responsibility [ 122 ]. Shifting caregiving tasks onto a technological device, which, by being a device and not a human carer, cannot be morally responsible in the same way as a human being can [ 123 ], may introduce a sense of void that caregivers are reluctant to create. Studies have shown that a mismatch in professional and personal values in nursing causes emotional discomfort and stress [ 124 ], therefore the shift in the professional environment caused by SHHTs is likely to be met with aversion. Additionally, the negative impact of SHHTs on caregiving responsibility was also tied to practical concerns, like not having enough time to learn how to use the technology by the caregivers [ 35 ], or needing to have access to and checking the older person’s health data [ 36 ]. Such concerns point to the possibility that SHHTs can create unforeseen tasks, which could turn into true burdens, instead of alleviating caregivers. Indeed, there are indications that the increase in information about the older person through monitoring technologies causes stress for both caregivers and older persons, as the former feel pressure to look at the available data, while the latter prefer to hide unfavorable information to not seem burdensome for their caregivers [ 125 ]. Another consequence of SHHTs that emerged as a sub-category was the renegotiation of responsibilities among the different stakeholders. In the field of (assistive) technology, this renegotiation is an ongoing process with efforts to make technology and its developers more accountable, through new policies and regulations [ 126 ]. In the realm of assistive technology in healthcare, these negotiations focus on high-risk cases and emergencies [ 127 ]. Who is responsible for the death of a person if the assistive technology failed to recognize an emergency, or to alert humans in time? Such issues around responsibility and legal liability are partially responsible for the slow uptake of technology in caregiving [ 128 ].

Another important but less discussed ethical concern was ageism and stigma. Ageist prejudices include being perceived as slow, useless, burdensome, and incompetent [ 129 ]. Fear of aging and becoming a burden to others is a fear many older persons have, as current social norms demand independence until death [ 130 ]. Furthermore, the general ubiquitous use of technology has possibly exacerbated the issue of ageism, as life became fast paced and more pressure is placed on aging persons to keep up [ 131 ]. While this would call for more attention to studying ageism in relation to technology, our findings indicate that, it does not unfortunately seem at the forefront of concerns that are prevalent in the literature (and thereby the society).

Related to ageism, is the wish of older persons to not be perceived as old and/or in the need of assistance (in the form of technology) explains the prevalent demand for unobtrusive technology. Obtrusiveness, in the context of SHHTs, is defined as “undesirably prominent and or/noticeable”, yet this definition should include the user’s perception and environment, and is thus not an objectively applicable definition [ 132 ]. Nevertheless, we can infer that by “unobtrusive”, users mean SHHTs that is not noticeable by them or, mostly importantly, by other persons to possibly reduce stigma associated with using a technology deemed to be for persons with certain limitations. Further research will have to confirm if unobtrusive technology actually reduces stigma and/or fosters acceptance of such SHHTs in caregiving.

Lastly, the sub-theme of stigmatization of women and immigrants in caregiving and possibly exacerbating their caregiving burden through technology was only discovered in two theoretical publications [ 47 , 71 ]. While it is well known that caregiving burden mostly falls upon women [ 133 , 134 ], many of them with a migration background when it comes to live-in caregivers [ 135 , 136 ]. It is surprising that we found no redistribution of burden of care with technology. This is likely due to the fact that caregiving – be it technologically assisted or not – remains perceived as a more feminine and, unfortunately, low status profession [ 137 ]. The development of technology, however, are still mostly associated with masculinity This tension between the innovators and actual users of technology can lead to the exacerbation of stigma for female and migrant caregivers, as the human bias is conserved by the technology, instead of disrupted through it [ 137 ].

Finally, trust was an expected ethical concern, given that it is a widely discussed topic in relation to technology (see for example, [ 123 , 138 ] and also in the context of nursing [ 95 , 139 ]. Older persons were trusting caregivers to understand SHHTs [ 48 ], while caregivers feared that older persons would not trust the used technology, even though said persons did not express such concerns [ 32 ]. A possibility to mitigate such misunderstandings and put both caregivers and care recipients on an equal understanding of the technology are education tools [ 140 ]. Another surprising finding was that some older persons were inclined to trust SHHTs even more than human caregivers, as they were seen as more reliable [ 70 ]. This trust in technology was increased when a physical robot instead of an only virtual agent was involved [ 60 , 65 ]. Studies in the realm of embodiment of virtual agents and robots suggest that the presence of a body or face promotes human-like interactions with said agents [ 51 ]. Furthermore, our systematic review discovered other characteristics which promote trust in SHHTs, such as perceived usefulness [ 94 ] or time spent with the technology [ 59 ]. Another important aspect is the already existing trust in the person introducing the technology to the user [ 34 , 93 ]. In combining these characteristics in the design and implementation of SHHTs in caregiving, researchers and technology developers need to find creative mechanisms to facilitate trustworthiness and foster adoption of new technologies in caregiving.

Limitations

While we searched 10 databases for publications over a span of 20 years, we are aware that older or newer publications will have escaped our systematic review. Relevant new literature that we have found when writing our results have been incorporated in this manuscript. Furthermore, as we specifically refrained from using terms related to ethics in our search strings to also capture the instances of absence of ethical concerns, this choice may have led to missing a few articles as a consequence, especially in regards to theoretical publications. Lastly, due to lack of resources, we were unable to carry out independent data extraction for all included papers (N = 156) and chose to validate the quality of extracted data by using a random selection of 10% of the included sample. Since there was high agreement on extracted data, we are confident about the quality of our study findings.

SHHTs offer the possibility to mitigate the shortage of human caregiving resources and to enable older persons to age in place, being adequately supported by technology. However, this shift in caregiving comes with ethical challenges. If and how these ethical challenges are mentioned in the current research around SHHTs in caregiving for older persons was the goal of this systematic review. Through analyzing 156 articles, both empirical and theoretical, we discovered that, while over one third of articles did not mention any ethical concerns whatsoever, the other two thirds discussed a plethora of ethical issues. Specifically, we discovered the emergence of concerns with the use of technology in the care of older persons around the theme of human vs. artificial relationships, ageism and stigma, and responsibility. In short, our systematic review offers a comprehensive overview of the currently discussed ethical issues in the context of SHHTs in caregiving for older persons. However, scholars in the fields of gerontology, ethics, and technology working on such issues would be already (or should be) aware that ethical concerns will change with each developing technology and the population it is used for. For instance, with the rise of Artificial intelligence/Machine Learning, new intelligent or smart technologies will continue to mature with use and time. Thus, ethical value such as autonomy will require re-evaluation with this significant content development as well as deciding, if the person would/should be asked to re-consent or how should this decision making proceed should he or she have developed dementia. In sum, more critical work is necessary to prospectively act on ethical concerns that may arise with new and developing technologies that could be used in reducing caregiving burden now and in the future.

Data Availability

All data generated or analyzed during this systematic review are included in this published article and its appendices. Appendix part 1 contains all included articles and their characteristics. Appendix part 2 contains the search strategy and all search strings for all searched databases, as well as the PROSPERO registration number.

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We thank the information specialist of the University of Basel who advised us on our search strategy.

Open access funding provided by University of Basel. This study was supported financially by the Swiss National Science Foundation (SNF NRP-77 Digital Transformation, Grant Number 407740_187464/1) as part of the SmaRt homES, Older adUlts, and caRegivers: Facilitating social aCceptance and negotiating rEsponsibilities [RESOURCE] project. The funder neither took part in the writing process, nor does any part of the views expressed in the review belong to the funder.

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Felber, N.A., Tian, Y., Pageau, F. et al. Mapping ethical issues in the use of smart home health technologies to care for older persons: a systematic review. BMC Med Ethics 24 , 24 (2023). https://doi.org/10.1186/s12910-023-00898-w

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The partisan balance has tightened in recent years following a clear edge in Democratic Party affiliation during the last administration.

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Partisans and partisan leaners in the U.S. electorate

About two-thirds of registered voters identify as a partisan, and they are roughly evenly split between those who say they are Republicans (32% of voters) and those who say they are Democrats (33%). Roughly a third instead say they are independents or something else (35%), with most of these voters leaning toward one of the parties. Partisan leaners often share the same political views and behaviors as those who directly identify with the party they favor.

The share of voters who identify as independent or something else is somewhat higher than in the late 1990s and early 2000s. As a result, there are more “leaners” today than in the past. Currently, 15% of voters lean toward the Republican Party and 16% lean toward the Democratic Party. By comparison, in 1994, 27% of voters leaned toward either the GOP (15%) or the Democratic Party (12%).

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A quarter of voters associate with the Democratic Party and describe their views as either conservative or moderate, and 14% identify as moderates or liberals and are Republicans or Republican leaners.

The partisan and ideological composition of voters is relatively unchanged over the last five years.

(As a result of significant mode differences in measures of ideology between telephone and online surveys, there is not directly comparable data on ideology prior to 2019.)

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Analysis finds most research underpinning clinical guidelines, hormone treatments and puberty blockers to be low quality

Review of gender services has major implications for mental health services

The head of the world’s largest review into children’s care has said that gender medicine is “built on shaky foundations”.

Dr Hilary Cass, the paediatrician commissioned to conduct a review of the services provided by the NHS to children and young people questioning their gender identity, said that while doctors tended to be cautious in implementing new findings in emerging areas of medicine, “quite the reverse happened in the field of gender care for children”.

Cass commissioned the University of York to conduct a series of analyses as part of her review.

Two papers examined the quality and development of current guidelines and recommendations for managing gender dysphoria in children and young people. Most of the 23 clinical guidelines reviewed were not independent or evidence based, the researchers found.

A third paper on puberty blockers found that of 50 studies, only one was of high quality.

Similarly, of 53 studies included in a fourth paper on the use of hormone treatment, only one was of sufficiently high quality, with little or only inconsistent evidence on key outcomes.

Here are the main findings of the reviews:

Clinical guidelines

Increasing numbers of children and young people experiencing gender dysphoria are being referred to specialist gender services. There are various guidelines outlining approaches to the clinical care of these children and adolescents.

In the first two papers, the York researchers examined the quality and development of published guidelines or clinical guidance containing recommendations for managing gender dysphoria in children and young people up to the age of 18.

They studied a total of 23 guidelines published in different countries between 1998 and 2022. All but two were published after 2010.

Most of them lacked “an independent and evidence-based approach and information about how recommendations were developed”, the researchers said.

Few guidelines were informed by a systematic review of empirical evidence and they lack transparency about how their recommendations were developed. Only two reported consulting directly with children and young people during their development, the York academics found.

“Healthcare services and professionals should take into account the poor quality and interrelated nature of published guidance to support the management of children and adolescents experiencing gender dysphoria/incongruence,” the researchers wrote.

Writing in the British Medical Journal (BMJ) , Cass said that while medicine was usually based on the pillars of integrating the best available research evidence with clinical expertise, and patient values and preferences, she “found that in gender medicine those pillars are built on shaky foundations”.

She said the World Professional Association of Transgender Healthcare (WPATH) had been “highly influential in directing international practice, although its guidelines were found by the University of York’s appraisal to lack developmental rigour and transparency”.

In the foreword to her report, Cass said while doctors tended to be cautious in implementing new findings “quite the reverse happened in the field of gender care for children”.

In one example, she said a single Dutch medical study, “suggesting puberty blockers may improve psychological wellbeing for a narrowly defined group of children with gender incongruence”, had formed the basis for their use to “spread at pace to other countries”. Subsequently, there was a “greater readiness to start masculinising/feminising hormones in mid-teens”.

She added: “Some practitioners abandoned normal clinical approaches to holistic assessment, which has meant that this group of young people have been exceptionalised compared to other young people with similarly complex presentations. They deserve very much better.”

Both papers repeatedly pointed to a key problem in this area of medicine: a dearth of good data.

She said: “Filling this knowledge gap would be of great help to the young people wanting to make informed choices about their treatment.”

Cass said the NHS should put in place a “full programme of research” looking at the characteristics, interventions and outcomes of every young person presenting to gender services, with consent routinely sought for enrolment in a research study that followed them into adulthood.

Gender medicine was “an area of remarkably weak evidence”, her review found, with study results also “exaggerated or misrepresented by people on all sides of the debate to support their viewpoint”.

Alongside a puberty blocker trial, which could be in place by December, there should be research into psychosocial interventions and the use of the masculinising and feminising hormones testosterone and oestrogen, the review found.

Hormone treatment

Many trans people who seek medical intervention in their transition opt to take hormones to masculinise or feminise their body, an approach that has been used in transgender adults for decades.

“It is a well-established practice that has transformed the lives of many transgender people,” the Cass review notes, adding that while these drugs are not without long-term problems and side-effects, for many they are dramatically outweighed by the benefits.

For birth-registered females, the approach means taking testosterone, which brings about changes including the growth of facial hair and a deepening of the voice, while for birth-registered males, it involves taking hormones including oestrogen to promote changes including the growth of breasts and an increase in body fat. Some of these changes may be irreversible.

However, in recent years a growing proportion of adolescents have begun taking these cross-sex, or gender-affirming, hormones, with the vast majority who are prescribed puberty blockers subsequently moving on to such medication.

This growing take-up among young people has led to questions over the impact of these hormones in areas ranging from mental health to sexual functioning and fertility.

Now researchers at the University of York have carried out a review of the evidence, comprising an analysis of 53 previously published studies, in an attempt to set out what is known – and what is not – about the risks, benefits and possible side-effects of such hormones on young people.

All but one study, which looked at side-effects, were rated of moderate or low quality, with the researchers finding limited evidence for the impact of such hormones on trans adolescents with respect to outcomes, including gender dysphoria and body satisfaction.

The researchers noted inconsistent findings around the impact of such hormones on growth, height, bone health and cardiometabolic effects, such as BMI and cholesterol markers. In addition, they found no study assessed fertility in birth-registered females, and only one looked at fertility in birth-registered males.

“These findings add to other systematic reviews in concluding there is insufficient and/or inconsistent evidence about the risks and benefits of hormone interventions in this population,” the authors write.

However, the review did find some evidence that masculinising or feminising hormones might help with psychological health in young trans people. An analysis of five studies in the area suggested hormone treatment may improve depression, anxiety and other aspects of mental health in adolescents after 12 months of treatment, with three of four studies reporting an improvement around suicidality and/or self-harm (one reported no change).

But unpicking the precise role of such hormones is difficult. “Most studies included adolescents who received puberty suppression, making it difficult to determine the effects of hormones alone,” the authors write, adding that robust research on psychological health with long-term follow-up was needed.

The Cass review has recommended NHS England should review the current policy on masculinising or feminising hormones, advising that while there should be the option to provide such drugs from age 16, extreme caution was recommended, and there should be a clear clinical rationale for not waiting until an individual reached 18.

Puberty blockers

Treatments to suppress puberty in adolescents became available through routine clinical practice in the UK a decade ago.

While the drugs have long been used to treat precocious puberty – when children start puberty at an extremely young age – they have only been used off-label in children with gender dysphoria or incongruence since the late 1990s. The rationale for giving puberty blockers, which originated in the Netherlands, was to buy thinking time for young people and improve their ability to smooth their transition in later life.

Data from gender clinics reported in the Cass review showed the vast majority of people who started puberty suppression went on to have masculinising or feminising hormones, suggesting that puberty blockers did not buy people time to think.

To understand the broader effects of puberty blockers, researchers at the University of York identified 50 papers that reported on the effects of the drugs in adolescents with gender dysphoria or incongruence. According to their systematic review, only one of these studies was high quality, with a further 25 papers regarded as moderate quality. The remaining 24 were deemed too weak to be included in the analysis.

Many of the reports looked at how well puberty was suppressed and the treatment’s side-effects, but fewer looked at whether the drugs had their intended benefits.

Of two studies that investigated gender dysphoria and body satisfaction, neither found a change after receiving puberty blockers. The York team found “very limited” evidence that puberty blockers improved mental health.

Overall, the researchers said “no conclusions” could be drawn about the impact on gender dysphoria, mental and psychosocial health or cognitive development, though there was some evidence bone health and height may be compromised during treatment.

Based on the York work, the Cass review finds that puberty blockers offer no obvious benefit in helping transgender males to help their transition in later life, particularly if the drugs do not lead to an increase in height in adult life. For transgender females, the benefits of stopping irreversible changes such as a deeper voice and facial hair have to be weighed up against the need for penile growth should the person opt for vaginoplasty, the creation of a vagina and vulva.

In March, NHS England announced that children with gender dysphoria would no longer receive puberty blockers as routine practice. Instead, their use will be confined to a trial that the Cass review says should form part of a broader research programme into the effects of masculinising and feminising hormones.

• Transgender
• Young people

More on this story

Veteran trans campaigner: ‘Cass review has potential for positive change’

Cass review must be used as ‘watershed moment’ for NHS gender services, says Streeting

‘This isn’t how good scientific debate happens’: academics on culture of fear in gender medicine research

Five thousand children with gender-related distress awaiting NHS care in England

Ban on children’s puberty blockers to be enforced in private sector in England

What Cass review says about surge in children seeking gender services

Adult transgender clinics in England face inquiry into patient care

‘Children are being used as a football’: Hilary Cass on her review of gender identity services

Thousands of children unsure of gender identity ‘let down by NHS’, report finds

Most viewed

Research uncovers differences between men and women in sleep, circadian rhythms and metabolism

A new review of research evidence has explored the key differences in how women and men sleep, variations in their body clocks, and how this affects their metabolism.

Published in Sleep Medicine Reviews , the paper highlights the crucial role sex plays in understanding these factors and suggests a person's biological sex should be considered when treating sleep, circadian rhythm and metabolic disorders.

Differences in sleep

The review found women rate their sleep quality lower than men's and report more fluctuations in their quality of sleep, corresponding to changes throughout the menstrual cycle.

"Lower sleep quality is associated with anxiety and depressive disorders, which are twice as common in women as in men," says Dr Sarah L. Chellappa from the University of Southampton and senior author of the paper. "Women are also more likely than men to be diagnosed with insomnia, although the reasons are not entirely clear. Recognising and comprehending sex differences in sleep and circadian rhythms is essential for tailoring approaches and treatment strategies for sleep disorders and associated mental health conditions."

The paper's authors also found women have a 25 to 50 per cent higher likelihood of developing restless legs syndrome and are up to four times as likely to develop sleep-related eating disorder, where people eat repeatedly during the night.

Meanwhile, men are three times more likely to be diagnosed with obstructive sleep apnoea (OSA). OSA manifests differently in women and men, which might explain this disparity. OSA is associated with a heightened risk of heart failure in women, but not men.

Sleep lab studies found women sleep more than men, spending around 8 minutes longer in non-REM (Rapid Eye Movement) sleep, where brain activity slows down. While the time we spend in NREM declines with age, this decline is more substantial in older men. Women also entered REM sleep, characterised by high levels of brain activity and vivid dreaming, earlier than men.

Variations in body clocks

The team of all women researchers from the University of Southampton in the UK, and Stanford University and Harvard University in the United States, found differences between the sexes are also present in our circadian rhythms.

They found melatonin, a hormone that helps with the timing of circadian rhythms and sleep, is secreted earlier in women than men. Core body temperature, which is at its highest before sleep and its lowest a few hours before waking, follows a similar pattern, reaching its peak earlier in women than in men.

Corresponding to these findings, other studies suggest women's intrinsic circadian periods are shorter than men's by around six minutes.

Dr Renske Lok from Stanford University, who led the review, says: "While this difference may be small, it is significant. The misalignment between the central body clock and the sleep/wake cycle is approximately five times larger in women than in men. Imagine if someone's watch was consistently running six minutes faster or slower. Over the course of days, weeks, and months, this difference can lead to a noticeable misalignment between the internal clock and external cues, such as light and darkness.

"Disruptions in circadian rhythms have been linked to various health problems, including sleep disorders, mood disorders and impaired cognitive function. Even minor differences in circadian periods can have significant implications for overall health and well-being."

Men tend to be later chronotypes, preferring to go to bed and wake up later than women. This may lead to social jet lag, where their circadian rhythm doesn't align with social demands, like work. They also have less consistent rest-activity schedules than women on a day-to-day basis.

Impact on metabolism

The research team also investigated if the global increase in obesity might be partially related to people not getting enough sleep -- with 30 per cent of 30- to 64-year-olds sleeping less than six hours a night in the United States, with similar numbers in Europe.

There were big differences between how women's and men's brains responded to pictures of food after sleep deprivation. Brain networks associated with cognitive (decision making) and affective (emotional) processes were twice as active in women than in men. Another study found women had a 1.5 times higher activation in the limbic region (involved in emotion processing, memory formation, and behavioural regulation) in response to images of sweet food compared to men.

Despite this difference in brain activity, men tend to overeat more than women in response to sleep loss. Another study found more fragmented sleep, taking longer to get to sleep, and spending more time in bed trying to get to sleep were only associated with more hunger in men.

Both women and men nightshift workers are more likely to develop type 2 diabetes, but this risk is higher in men. Sixty-six per cent of women nightshift workers experienced emotional eating and another study suggests they are around 1.5 times more likely to be overweight or obese compared to women working day shifts.

The researchers also found emerging evidence on how women and men respond differently to treatments for sleep and circadian disorders. For example, weight loss was more successful in treating women with OSA than men, while women prescribed zolpidem (an insomnia medication) may require a lower dosage than men to avoid lingering sleepiness the next morning.

Dr Chellappa added: "Most of sleep and circadian interventions are a newly emerging field with limited research on sex differences. As we understand more about how women and men sleep, differences in their circadian rhythms and how these affect their metabolism, we can move towards more precise and personalised healthcare which enhances the likelihood of positive outcomes."

The research was funded by the Alexander Von Humboldt Foundation, the US Department of Defense and the National Institute of Health.

• Sleep Disorder Research
• Insomnia Research
• Gender Difference
• Sleep Disorders
• Obstructive Sleep Apnea
• Circadian rhythm sleep disorder
• Glutamic acid
• Sleep deprivation

Story Source:

Materials provided by University of Southampton . Note: Content may be edited for style and length.

Journal Reference :

• Renske Lok, Jingyi Qian, Sarah L. Chellappa. Sex differences in sleep, circadian rhythms, and metabolism: Implications for precision medicine . Sleep Medicine Reviews , 2024; 75: 101926 DOI: 10.1016/j.smrv.2024.101926

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Introduction to systematic review and meta-analysis

1 Department of Anesthesiology and Pain Medicine, Inje University Seoul Paik Hospital, Seoul, Korea

2 Department of Anesthesiology and Pain Medicine, Chung-Ang University College of Medicine, Seoul, Korea

Systematic reviews and meta-analyses present results by combining and analyzing data from different studies conducted on similar research topics. In recent years, systematic reviews and meta-analyses have been actively performed in various fields including anesthesiology. These research methods are powerful tools that can overcome the difficulties in performing large-scale randomized controlled trials. However, the inclusion of studies with any biases or improperly assessed quality of evidence in systematic reviews and meta-analyses could yield misleading results. Therefore, various guidelines have been suggested for conducting systematic reviews and meta-analyses to help standardize them and improve their quality. Nonetheless, accepting the conclusions of many studies without understanding the meta-analysis can be dangerous. Therefore, this article provides an easy introduction to clinicians on performing and understanding meta-analyses.

Introduction

A systematic review collects all possible studies related to a given topic and design, and reviews and analyzes their results [ 1 ]. During the systematic review process, the quality of studies is evaluated, and a statistical meta-analysis of the study results is conducted on the basis of their quality. A meta-analysis is a valid, objective, and scientific method of analyzing and combining different results. Usually, in order to obtain more reliable results, a meta-analysis is mainly conducted on randomized controlled trials (RCTs), which have a high level of evidence [ 2 ] ( Fig. 1 ). Since 1999, various papers have presented guidelines for reporting meta-analyses of RCTs. Following the Quality of Reporting of Meta-analyses (QUORUM) statement [ 3 ], and the appearance of registers such as Cochrane Library’s Methodology Register, a large number of systematic literature reviews have been registered. In 2009, the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement [ 4 ] was published, and it greatly helped standardize and improve the quality of systematic reviews and meta-analyses [ 5 ].

Levels of evidence.

In anesthesiology, the importance of systematic reviews and meta-analyses has been highlighted, and they provide diagnostic and therapeutic value to various areas, including not only perioperative management but also intensive care and outpatient anesthesia [6–13]. Systematic reviews and meta-analyses include various topics, such as comparing various treatments of postoperative nausea and vomiting [ 14 , 15 ], comparing general anesthesia and regional anesthesia [ 16 – 18 ], comparing airway maintenance devices [ 8 , 19 ], comparing various methods of postoperative pain control (e.g., patient-controlled analgesia pumps, nerve block, or analgesics) [ 20 – 23 ], comparing the precision of various monitoring instruments [ 7 ], and meta-analysis of dose-response in various drugs [ 12 ].

Thus, literature reviews and meta-analyses are being conducted in diverse medical fields, and the aim of highlighting their importance is to help better extract accurate, good quality data from the flood of data being produced. However, a lack of understanding about systematic reviews and meta-analyses can lead to incorrect outcomes being derived from the review and analysis processes. If readers indiscriminately accept the results of the many meta-analyses that are published, incorrect data may be obtained. Therefore, in this review, we aim to describe the contents and methods used in systematic reviews and meta-analyses in a way that is easy to understand for future authors and readers of systematic review and meta-analysis.

Study Planning

It is easy to confuse systematic reviews and meta-analyses. A systematic review is an objective, reproducible method to find answers to a certain research question, by collecting all available studies related to that question and reviewing and analyzing their results. A meta-analysis differs from a systematic review in that it uses statistical methods on estimates from two or more different studies to form a pooled estimate [ 1 ]. Following a systematic review, if it is not possible to form a pooled estimate, it can be published as is without progressing to a meta-analysis; however, if it is possible to form a pooled estimate from the extracted data, a meta-analysis can be attempted. Systematic reviews and meta-analyses usually proceed according to the flowchart presented in Fig. 2 . We explain each of the stages below.

Flowchart illustrating a systematic review.

Formulating research questions

A systematic review attempts to gather all available empirical research by using clearly defined, systematic methods to obtain answers to a specific question. A meta-analysis is the statistical process of analyzing and combining results from several similar studies. Here, the definition of the word “similar” is not made clear, but when selecting a topic for the meta-analysis, it is essential to ensure that the different studies present data that can be combined. If the studies contain data on the same topic that can be combined, a meta-analysis can even be performed using data from only two studies. However, study selection via a systematic review is a precondition for performing a meta-analysis, and it is important to clearly define the Population, Intervention, Comparison, Outcomes (PICO) parameters that are central to evidence-based research. In addition, selection of the research topic is based on logical evidence, and it is important to select a topic that is familiar to readers without clearly confirmed the evidence [ 24 ].

Protocols and registration

In systematic reviews, prior registration of a detailed research plan is very important. In order to make the research process transparent, primary/secondary outcomes and methods are set in advance, and in the event of changes to the method, other researchers and readers are informed when, how, and why. Many studies are registered with an organization like PROSPERO ( http://www.crd.york.ac.uk/PROSPERO/ ), and the registration number is recorded when reporting the study, in order to share the protocol at the time of planning.

Defining inclusion and exclusion criteria

Information is included on the study design, patient characteristics, publication status (published or unpublished), language used, and research period. If there is a discrepancy between the number of patients included in the study and the number of patients included in the analysis, this needs to be clearly explained while describing the patient characteristics, to avoid confusing the reader.

Literature search and study selection

In order to secure proper basis for evidence-based research, it is essential to perform a broad search that includes as many studies as possible that meet the inclusion and exclusion criteria. Typically, the three bibliographic databases Medline, Embase, and Cochrane Central Register of Controlled Trials (CENTRAL) are used. In domestic studies, the Korean databases KoreaMed, KMBASE, and RISS4U may be included. Effort is required to identify not only published studies but also abstracts, ongoing studies, and studies awaiting publication. Among the studies retrieved in the search, the researchers remove duplicate studies, select studies that meet the inclusion/exclusion criteria based on the abstracts, and then make the final selection of studies based on their full text. In order to maintain transparency and objectivity throughout this process, study selection is conducted independently by at least two investigators. When there is a inconsistency in opinions, intervention is required via debate or by a third reviewer. The methods for this process also need to be planned in advance. It is essential to ensure the reproducibility of the literature selection process [ 25 ].

Quality of evidence

However, well planned the systematic review or meta-analysis is, if the quality of evidence in the studies is low, the quality of the meta-analysis decreases and incorrect results can be obtained [ 26 ]. Even when using randomized studies with a high quality of evidence, evaluating the quality of evidence precisely helps determine the strength of recommendations in the meta-analysis. One method of evaluating the quality of evidence in non-randomized studies is the Newcastle-Ottawa Scale, provided by the Ottawa Hospital Research Institute 1) . However, we are mostly focusing on meta-analyses that use randomized studies.

If the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) system ( http://www.gradeworkinggroup.org/ ) is used, the quality of evidence is evaluated on the basis of the study limitations, inaccuracies, incompleteness of outcome data, indirectness of evidence, and risk of publication bias, and this is used to determine the strength of recommendations [ 27 ]. As shown in Table 1 , the study limitations are evaluated using the “risk of bias” method proposed by Cochrane 2) . This method classifies bias in randomized studies as “low,” “high,” or “unclear” on the basis of the presence or absence of six processes (random sequence generation, allocation concealment, blinding participants or investigators, incomplete outcome data, selective reporting, and other biases) [ 28 ].

The Cochrane Collaboration’s Tool for Assessing the Risk of Bias [ 28 ]

Data extraction

Two different investigators extract data based on the objectives and form of the study; thereafter, the extracted data are reviewed. Since the size and format of each variable are different, the size and format of the outcomes are also different, and slight changes may be required when combining the data [ 29 ]. If there are differences in the size and format of the outcome variables that cause difficulties combining the data, such as the use of different evaluation instruments or different evaluation timepoints, the analysis may be limited to a systematic review. The investigators resolve differences of opinion by debate, and if they fail to reach a consensus, a third-reviewer is consulted.

Data Analysis

The aim of a meta-analysis is to derive a conclusion with increased power and accuracy than what could not be able to achieve in individual studies. Therefore, before analysis, it is crucial to evaluate the direction of effect, size of effect, homogeneity of effects among studies, and strength of evidence [ 30 ]. Thereafter, the data are reviewed qualitatively and quantitatively. If it is determined that the different research outcomes cannot be combined, all the results and characteristics of the individual studies are displayed in a table or in a descriptive form; this is referred to as a qualitative review. A meta-analysis is a quantitative review, in which the clinical effectiveness is evaluated by calculating the weighted pooled estimate for the interventions in at least two separate studies.

The pooled estimate is the outcome of the meta-analysis, and is typically explained using a forest plot ( Figs. 3 and ​ and4). 4 ). The black squares in the forest plot are the odds ratios (ORs) and 95% confidence intervals in each study. The area of the squares represents the weight reflected in the meta-analysis. The black diamond represents the OR and 95% confidence interval calculated across all the included studies. The bold vertical line represents a lack of therapeutic effect (OR = 1); if the confidence interval includes OR = 1, it means no significant difference was found between the treatment and control groups.

Forest plot analyzed by two different models using the same data. (A) Fixed-effect model. (B) Random-effect model. The figure depicts individual trials as filled squares with the relative sample size and the solid line as the 95% confidence interval of the difference. The diamond shape indicates the pooled estimate and uncertainty for the combined effect. The vertical line indicates the treatment group shows no effect (OR = 1). Moreover, if the confidence interval includes 1, then the result shows no evidence of difference between the treatment and control groups.

Forest plot representing homogeneous data.

Dichotomous variables and continuous variables

In data analysis, outcome variables can be considered broadly in terms of dichotomous variables and continuous variables. When combining data from continuous variables, the mean difference (MD) and standardized mean difference (SMD) are used ( Table 2 ).

Summary of Meta-analysis Methods Available in RevMan [ 28 ]

The MD is the absolute difference in mean values between the groups, and the SMD is the mean difference between groups divided by the standard deviation. When results are presented in the same units, the MD can be used, but when results are presented in different units, the SMD should be used. When the MD is used, the combined units must be shown. A value of “0” for the MD or SMD indicates that the effects of the new treatment method and the existing treatment method are the same. A value lower than “0” means the new treatment method is less effective than the existing method, and a value greater than “0” means the new treatment is more effective than the existing method.

When combining data for dichotomous variables, the OR, risk ratio (RR), or risk difference (RD) can be used. The RR and RD can be used for RCTs, quasi-experimental studies, or cohort studies, and the OR can be used for other case-control studies or cross-sectional studies. However, because the OR is difficult to interpret, using the RR and RD, if possible, is recommended. If the outcome variable is a dichotomous variable, it can be presented as the number needed to treat (NNT), which is the minimum number of patients who need to be treated in the intervention group, compared to the control group, for a given event to occur in at least one patient. Based on Table 3 , in an RCT, if x is the probability of the event occurring in the control group and y is the probability of the event occurring in the intervention group, then x = c/(c + d), y = a/(a + b), and the absolute risk reduction (ARR) = x − y. NNT can be obtained as the reciprocal, 1/ARR.

Calculation of the Number Needed to Treat in the Dichotomous table

Fixed-effect models and random-effect models

In order to analyze effect size, two types of models can be used: a fixed-effect model or a random-effect model. A fixed-effect model assumes that the effect of treatment is the same, and that variation between results in different studies is due to random error. Thus, a fixed-effect model can be used when the studies are considered to have the same design and methodology, or when the variability in results within a study is small, and the variance is thought to be due to random error. Three common methods are used for weighted estimation in a fixed-effect model: 1) inverse variance-weighted estimation 3) , 2) Mantel-Haenszel estimation 4) , and 3) Peto estimation 5) .

A random-effect model assumes heterogeneity between the studies being combined, and these models are used when the studies are assumed different, even if a heterogeneity test does not show a significant result. Unlike a fixed-effect model, a random-effect model assumes that the size of the effect of treatment differs among studies. Thus, differences in variation among studies are thought to be due to not only random error but also between-study variability in results. Therefore, weight does not decrease greatly for studies with a small number of patients. Among methods for weighted estimation in a random-effect model, the DerSimonian and Laird method 6) is mostly used for dichotomous variables, as the simplest method, while inverse variance-weighted estimation is used for continuous variables, as with fixed-effect models. These four methods are all used in Review Manager software (The Cochrane Collaboration, UK), and are described in a study by Deeks et al. [ 31 ] ( Table 2 ). However, when the number of studies included in the analysis is less than 10, the Hartung-Knapp-Sidik-Jonkman method 7) can better reduce the risk of type 1 error than does the DerSimonian and Laird method [ 32 ].

Fig. 3 shows the results of analyzing outcome data using a fixed-effect model (A) and a random-effect model (B). As shown in Fig. 3 , while the results from large studies are weighted more heavily in the fixed-effect model, studies are given relatively similar weights irrespective of study size in the random-effect model. Although identical data were being analyzed, as shown in Fig. 3 , the significant result in the fixed-effect model was no longer significant in the random-effect model. One representative example of the small study effect in a random-effect model is the meta-analysis by Li et al. [ 33 ]. In a large-scale study, intravenous injection of magnesium was unrelated to acute myocardial infarction, but in the random-effect model, which included numerous small studies, the small study effect resulted in an association being found between intravenous injection of magnesium and myocardial infarction. This small study effect can be controlled for by using a sensitivity analysis, which is performed to examine the contribution of each of the included studies to the final meta-analysis result. In particular, when heterogeneity is suspected in the study methods or results, by changing certain data or analytical methods, this method makes it possible to verify whether the changes affect the robustness of the results, and to examine the causes of such effects [ 34 ].

Heterogeneity

Homogeneity test is a method whether the degree of heterogeneity is greater than would be expected to occur naturally when the effect size calculated from several studies is higher than the sampling error. This makes it possible to test whether the effect size calculated from several studies is the same. Three types of homogeneity tests can be used: 1) forest plot, 2) Cochrane’s Q test (chi-squared), and 3) Higgins I 2 statistics. In the forest plot, as shown in Fig. 4 , greater overlap between the confidence intervals indicates greater homogeneity. For the Q statistic, when the P value of the chi-squared test, calculated from the forest plot in Fig. 4 , is less than 0.1, it is considered to show statistical heterogeneity and a random-effect can be used. Finally, I 2 can be used [ 35 ].

I 2 , calculated as shown above, returns a value between 0 and 100%. A value less than 25% is considered to show strong homogeneity, a value of 50% is average, and a value greater than 75% indicates strong heterogeneity.

Even when the data cannot be shown to be homogeneous, a fixed-effect model can be used, ignoring the heterogeneity, and all the study results can be presented individually, without combining them. However, in many cases, a random-effect model is applied, as described above, and a subgroup analysis or meta-regression analysis is performed to explain the heterogeneity. In a subgroup analysis, the data are divided into subgroups that are expected to be homogeneous, and these subgroups are analyzed. This needs to be planned in the predetermined protocol before starting the meta-analysis. A meta-regression analysis is similar to a normal regression analysis, except that the heterogeneity between studies is modeled. This process involves performing a regression analysis of the pooled estimate for covariance at the study level, and so it is usually not considered when the number of studies is less than 10. Here, univariate and multivariate regression analyses can both be considered.

Publication bias

Publication bias is the most common type of reporting bias in meta-analyses. This refers to the distortion of meta-analysis outcomes due to the higher likelihood of publication of statistically significant studies rather than non-significant studies. In order to test the presence or absence of publication bias, first, a funnel plot can be used ( Fig. 5 ). Studies are plotted on a scatter plot with effect size on the x-axis and precision or total sample size on the y-axis. If the points form an upside-down funnel shape, with a broad base that narrows towards the top of the plot, this indicates the absence of a publication bias ( Fig. 5A ) [ 29 , 36 ]. On the other hand, if the plot shows an asymmetric shape, with no points on one side of the graph, then publication bias can be suspected ( Fig. 5B ). Second, to test publication bias statistically, Begg and Mazumdar’s rank correlation test 8) [ 37 ] or Egger’s test 9) [ 29 ] can be used. If publication bias is detected, the trim-and-fill method 10) can be used to correct the bias [ 38 ]. Fig. 6 displays results that show publication bias in Egger’s test, which has then been corrected using the trim-and-fill method using Comprehensive Meta-Analysis software (Biostat, USA).

Funnel plot showing the effect size on the x-axis and sample size on the y-axis as a scatter plot. (A) Funnel plot without publication bias. The individual plots are broader at the bottom and narrower at the top. (B) Funnel plot with publication bias. The individual plots are located asymmetrically.

Funnel plot adjusted using the trim-and-fill method. White circles: comparisons included. Black circles: inputted comparisons using the trim-and-fill method. White diamond: pooled observed log risk ratio. Black diamond: pooled inputted log risk ratio.

Result Presentation

When reporting the results of a systematic review or meta-analysis, the analytical content and methods should be described in detail. First, a flowchart is displayed with the literature search and selection process according to the inclusion/exclusion criteria. Second, a table is shown with the characteristics of the included studies. A table should also be included with information related to the quality of evidence, such as GRADE ( Table 4 ). Third, the results of data analysis are shown in a forest plot and funnel plot. Fourth, if the results use dichotomous data, the NNT values can be reported, as described above.

The GRADE Evidence Quality for Each Outcome

N: number of studies, ROB: risk of bias, PON: postoperative nausea, POV: postoperative vomiting, PONV: postoperative nausea and vomiting, CI: confidence interval, RR: risk ratio, AR: absolute risk.

When Review Manager software (The Cochrane Collaboration, UK) is used for the analysis, two types of P values are given. The first is the P value from the z-test, which tests the null hypothesis that the intervention has no effect. The second P value is from the chi-squared test, which tests the null hypothesis for a lack of heterogeneity. The statistical result for the intervention effect, which is generally considered the most important result in meta-analyses, is the z-test P value.

A common mistake when reporting results is, given a z-test P value greater than 0.05, to say there was “no statistical significance” or “no difference.” When evaluating statistical significance in a meta-analysis, a P value lower than 0.05 can be explained as “a significant difference in the effects of the two treatment methods.” However, the P value may appear non-significant whether or not there is a difference between the two treatment methods. In such a situation, it is better to announce “there was no strong evidence for an effect,” and to present the P value and confidence intervals. Another common mistake is to think that a smaller P value is indicative of a more significant effect. In meta-analyses of large-scale studies, the P value is more greatly affected by the number of studies and patients included, rather than by the significance of the results; therefore, care should be taken when interpreting the results of a meta-analysis.

When performing a systematic literature review or meta-analysis, if the quality of studies is not properly evaluated or if proper methodology is not strictly applied, the results can be biased and the outcomes can be incorrect. However, when systematic reviews and meta-analyses are properly implemented, they can yield powerful results that could usually only be achieved using large-scale RCTs, which are difficult to perform in individual studies. As our understanding of evidence-based medicine increases and its importance is better appreciated, the number of systematic reviews and meta-analyses will keep increasing. However, indiscriminate acceptance of the results of all these meta-analyses can be dangerous, and hence, we recommend that their results be received critically on the basis of a more accurate understanding.

1) http://www.ohri.ca .

2) http://methods.cochrane.org/bias/assessing-risk-bias-included-studies .

3) The inverse variance-weighted estimation method is useful if the number of studies is small with large sample sizes.

4) The Mantel-Haenszel estimation method is useful if the number of studies is large with small sample sizes.

5) The Peto estimation method is useful if the event rate is low or one of the two groups shows zero incidence.

6) The most popular and simplest statistical method used in Review Manager and Comprehensive Meta-analysis software.

7) Alternative random-effect model meta-analysis that has more adequate error rates than does the common DerSimonian and Laird method, especially when the number of studies is small. However, even with the Hartung-Knapp-Sidik-Jonkman method, when there are less than five studies with very unequal sizes, extra caution is needed.

8) The Begg and Mazumdar rank correlation test uses the correlation between the ranks of effect sizes and the ranks of their variances [ 37 ].

9) The degree of funnel plot asymmetry as measured by the intercept from the regression of standard normal deviates against precision [ 29 ].

10) If there are more small studies on one side, we expect the suppression of studies on the other side. Trimming yields the adjusted effect size and reduces the variance of the effects by adding the original studies back into the analysis as a mirror image of each study.