Umbrella Reviews: Synthesizing Evidence from Multiple Meta-Analyses

An umbrella review is a systematic review of existing systematic reviews and meta-analyses that compiles and contrasts their findings on a single broad question. For researchers in life sciences and related fields, this method addresses a practical problem: the volume of published meta-analyses has grown so large that decision makers cannot reasonably read and compare them individually. An umbrella review treats each systematic review or meta-analysis as the unit of analysis instead of individual primary studies. This article explains what umbrella reviews are, how they differ from other evidence synthesis methods, and how to conduct one using a structured protocol template.

What Defines an Umbrella Review

The defining feature of an umbrella review is that it only considers the highest level of evidence, namely other systematic reviews and meta-analyses, as its analytical unit. This approach allows the findings of reviews relevant to a review question to be compared and contrasted. The methodology working group at the Joanna Briggs Institute developed formal guidance for conducting umbrella reviews, including how to handle diverse types of evidence, both quantitative and qualitative. Their work, published in the International Journal of Evidence-Based Healthcare, describes the essential elements of an umbrella review and the methods developed for its conduct.

The term "umbrella review" is one of several names used for syntheses of existing systematic reviews. Other names include overview of reviews, review of reviews, and meta-review. Regardless of the label, the core purpose remains the same: to provide decision makers with a consolidated view of what the accumulated review-level evidence says about a topic.

An umbrella review differs from a traditional systematic review in several important ways. A systematic review searches for and analyzes primary studies, such as randomized controlled trials or cohort studies. An umbrella review searches for and analyzes systematic reviews and meta-analyses themselves. This means the search strategy targets review databases and filters for publication types. The data extraction focuses on review characteristics, pooled effect estimates, heterogeneity measures, and quality ratings instead of individual participant data.

Why Umbrella Reviews Matter in Life Sciences

The life sciences have experienced an unprecedented accumulation of systematic reviews and meta-analyses. In some fields, multiple meta-analyses addressing the same question arrive at different conclusions, leaving clinicians and researchers uncertain about which synthesis to trust. Umbrella reviews address this problem by systematically identifying all relevant reviews, assessing their quality, and comparing their findings.

A published umbrella review on social media use and adolescent mental health illustrates this need. The authors noted that literature reviews on this topic had accumulated at an unprecedented rate, yet a higher level integration of the evidence was still lacking. Their umbrella review, covering reviews published between 2019 and mid-2021, identified 25 reviews including seven meta-analyses, nine systematic reviews, and nine narrative reviews. The results showed that most reviews interpreted the associations between social media use and mental health as weak or inconsistent, while a few qualified the same associations as substantial and deleterious. This divergence in interpretation across reviews is precisely the kind of situation where an umbrella review provides value.

Another example comes from the study of dietary sugar consumption and health. An umbrella review published in the BMJ identified 73 meta-analyses and 83 health outcomes from 8601 unique articles. The review detected significant harmful associations between dietary sugar consumption and 18 endocrine or metabolic outcomes, 10 cardiovascular outcomes, seven cancer outcomes, and 10 other outcomes. Without an umbrella review, a researcher would need to locate and read all 73 meta-analyses to reach this level of synthesis.

At a Glance: Umbrella Review Essentials

How Umbrella Reviews Differ from Meta-Analyses and Systematic Reviews

Researchers often ask how an umbrella review compares to a meta-analysis or a systematic review. The distinction is straightforward but important for study design.

A meta-analysis is a statistical technique that combines the results of multiple primary studies to produce a pooled effect estimate. Meta-analyses are often conducted within systematic reviews but can also stand alone. The unit of analysis is the primary study, and the output is a summary effect size with confidence intervals.

A systematic review is a structured process for identifying, evaluating, and synthesizing all available evidence on a specific question. Systematic reviews may or may not include meta-analysis depending on whether the included studies are sufficiently similar to justify statistical pooling. The unit of analysis is again the primary study.

An umbrella review sits above both of these. Its unit of analysis is the systematic review or meta-analysis itself. instead of pooling primary study data, an umbrella review compares and contrasts the conclusions of existing reviews. This allows researchers to answer questions such as: Do different meta-analyses on the same topic agree? Which reviews are of sufficient quality to inform decisions? What explains discrepancies between review conclusions?

A practical example comes from an umbrella review of prehabilitation in adult patients undergoing surgery. The authors described their work as a systematic review of systematic reviews and synthesized evidence from 55 systematic reviews identified from 1412 titles. Their goal was to evaluate the certainty that prehabilitation improves postoperative outcomes, a question that no single meta-analysis could answer with confidence.

Core Principles of Umbrella Review Methodology

The methodology for umbrella reviews follows a structured set of principles that distinguish it from other forms of evidence synthesis. These principles ensure that the resulting review is transparent, reproducible, and useful for decision making.

Defining the Review Question

The review question must be broad enough to capture multiple systematic reviews but focused enough to be meaningful. A well formulated question specifies the population, intervention or exposure, comparator, and outcomes of interest. For example, an umbrella review on dietary sugar consumption and health defined its scope as all health outcomes in humans free from acute or chronic diseases, which allowed the inclusion of 73 meta-analyses covering 83 health outcomes.

Searching for Systematic Reviews

The search strategy for an umbrella review targets databases that index systematic reviews and meta-analyses. Common sources include PubMed, Embase, Web of Science, the Cochrane Database of Systematic Reviews, and the Joanna Briggs Institute database. Some umbrella reviews also search grey literature sources and trial registries. The search should be documented in enough detail that another researcher could reproduce it.

An umbrella review on the effects of maternal nutritional supplements and placental complications performed a systematic search across seven electronic databases, the PROSPERO register, and reference lists of identified papers. The results were screened in a three stage process based on title, abstract, and full text by two independent reviewers. This level of rigor is standard for umbrella review methodology.

Selecting Eligible Reviews

Inclusion and exclusion criteria must be established before screening begins. Typical inclusion criteria specify that reviews must be systematic reviews or meta-analyses, must address the review question, and must report on relevant outcomes. Exclusion criteria often include narrative reviews, conference abstracts, and primary studies.

An umbrella review on predicting falls in older adults included narrative reviews and systematic reviews with or without meta-analyses of all study types. The authors screened 2736 articles and ultimately included 31 reviews, 11 of which were meta-analyses. This example shows that umbrella reviews can accommodate different review types as long as they meet the eligibility criteria.

Assessing Methodological Quality

Quality assessment is a critical step in umbrella reviews because the conclusions drawn from a review are only as trustworthy as the methods used to produce it. Common tools include AMSTAR 2, which stands for A Measurement Tool to Assess Systematic Reviews version 2, and ROBIS, which stands for Risk of Bias Assessment Tool for Systematic Reviews.

An umbrella review on robot-assisted versus open kidney transplantation assessed methodological quality using the AMSTAR 2 tool and found that the six included studies were of low to moderate quality. This assessment allowed the authors to interpret their findings with appropriate caution and to highlight the need for high quality prospective studies.

Grading the Evidence

Evidence grading communicates the certainty of the findings to decision makers. The GRADE approach, which stands for Grading of Recommendations Assessment, Development and Evaluation, is commonly used. Some umbrella reviews apply their own classification systems based on statistical significance, heterogeneity, prediction intervals, small study effects, and excess significance bias.

An umbrella review on risk factors for endometrial cancer graded evidence as strong, highly suggestive, suggestive, or weak based on statistical significance of random effects summary estimates, the largest study included, number of cases, between study heterogeneity, 95 percent prediction intervals, small study effects, excess significance bias, and sensitivity analysis with credibility ceilings. Of 127 meta-analyses including cohort studies, only three associations were graded with strong evidence. This rigorous grading prevented the authors from overstating the importance of many proposed risk factors.

Practical Workflow for Conducting an Umbrella Review

Conducting an umbrella review requires careful planning and execution. The following workflow provides a structured approach that researchers can adapt to their specific topic.

Step 1: Formulate the Review Question and Register the Protocol

Begin by defining the review question using a structured framework such as PICO, which stands for Population, Intervention, Comparator, and Outcomes. The question should be broad enough to capture multiple systematic reviews but specific enough to be answerable. Register the protocol in a public registry such as PROSPERO to promote transparency and reduce duplication of effort.

An umbrella review on aromatherapy and sleep quality published its protocol in PLoS ONE, describing the planned search strategy, inclusion criteria, quality assessment methods, and statistical analysis approach. Publishing a protocol before conducting the review is considered best practice.

Step 2: Develop the Search Strategy

Design a search strategy that will identify systematic reviews and meta-analyses relevant to the review question. Search multiple databases to ensure comprehensive coverage. Common databases include PubMed, Embase, Web of Science, the Cochrane Database of Systematic Reviews, and the Joanna Briggs Institute database. Some reviews also search regional databases or databases in other languages.

An umbrella review on the health effects of various edible vegetable oils performed a comprehensive literature search across 12 databases for studies examining the association of different vegetable oils with health outcomes in adults. The search was conducted up to July 31, 2023, and identified 48 studies including 206 meta-analyses.

Step 3: Screen Titles and Abstracts

Screen the search results against the inclusion criteria in two stages. First, screen titles and abstracts to remove clearly irrelevant records. Second, retrieve full texts of potentially eligible reviews and screen them against the inclusion criteria. Two reviewers should perform screening independently, with disagreements resolved by discussion or by a third reviewer.

An umbrella review on the efficacy of psychological interventions for PTSD conducted a systematic search in MEDLINE, PsycINFO, PTSDpubs, Web of Science, and the Cochrane Database of Systematic Reviews. The authors contrasted all eligible meta-analyses irrespective of overlapping datasets to present a comprehensive overview of the state of research.

Step 4: Extract Data from Included Reviews

Develop a standardized data extraction form that captures the key characteristics of each included review. Typical data items include the review authors and year, the number and type of included primary studies, the population and intervention or exposure, the outcomes reported, the pooled effect estimates with confidence intervals, measures of heterogeneity, and the quality assessment results.

An umbrella review on nurse burnout extracted data using Microsoft Excel and analyzed the data with STATA 17.0. The authors measured heterogeneity using the I squared statistic and calculated summary prevalence estimates using the Der Simonian-Laird random effects model.

Step 5: Assess Quality and Certainty of Evidence

Apply a quality assessment tool to each included review. AMSTAR 2 is the most commonly used tool for this purpose. Some umbrella reviews also apply GRADE to assess the certainty of evidence for each outcome. The quality ratings should be reported transparently and used to inform the interpretation of findings.

An umbrella review on cadmium exposure and health outcomes used AMSTAR 2 to rate the quality of 79 non-overlapping studies. The results showed that 2 percent of meta-analyses were rated as high quality, 8 percent as moderate quality, 38 percent as low quality, and 33 percent as very low quality. This distribution is typical for many fields and underscores the importance of quality assessment in umbrella reviews.

Step 6: Assess Overlap of Primary Studies

Overlap occurs when the same primary study appears in multiple included reviews. High overlap can inflate the apparent strength of evidence because the same data are counted multiple times. The corrected covered area, or CCA, is a commonly used metric for quantifying overlap. The GROOVE tool, which stands for Graphical Representation of Overlap of OVErviews, can be used to visualize overlap.

An umbrella review on virtual reality for managing pain and fear and anxiety during pediatric needle procedures quantified primary study overlap using the corrected covered area and visualized it using the GROOVE approach. The CCA was 15.7 percent, indicating very high overlap among the 11 included meta-analyses containing 49 unique primary studies.

Step 7: Synthesize the Findings

Synthesize the findings from the included reviews using narrative synthesis, tabulation, or statistical methods. Narrative synthesis involves describing the findings of each review and comparing them across reviews. Tabulation involves presenting the key characteristics and findings of each review in a structured table. Statistical methods may include meta-analysis of review level effect estimates, as was done in some umbrella reviews.

An umbrella review on simulation technologies and virtual reality in enhancing empathy in health care education conducted a random effects meta-analysis of review level effect estimates. The meta-analysis of review level estimates demonstrated a moderate, statistically significant positive effect on empathy outcomes with a standardized mean difference of 0.43 and a 95 percent confidence interval of 0.37 to 0.50.

Step 8: Report the Umbrella Review

Report the umbrella review following established reporting guidelines. The PRISMA statement, which stands for Preferred Reporting Items for Systematic Reviews and Meta-Analyses, provides guidance for reporting systematic reviews and can be adapted for umbrella reviews. The EQUATOR Network maintains a comprehensive collection of reporting guidelines for health research.

The EQUATOR Network is an international initiative that seeks to improve the reliability and value of published health research literature by promoting transparent and accurate reporting. Researchers should consult the EQUATOR Network website to identify the appropriate reporting guideline for their review type.

Options and Tradeoffs in Umbrella Review Design

Umbrella reviews can be designed in several ways, and each design choice involves tradeoffs that researchers should consider carefully.

Including Only Meta-Analyses versus All Systematic Reviews

Some umbrella reviews include only meta-analyses because these provide quantitative pooled estimates that can be compared statistically. Other umbrella reviews include all systematic reviews, including those without meta-analysis, to capture a broader range of evidence. The tradeoff is between quantitative comparability and comprehensiveness.

An umbrella review on the effectiveness of irrigation protocols in endodontic therapy included four descriptive systematic reviews and nine meta-analyses. The authors conducted quantitative comparability between the meta-analyses while also describing the findings of the systematic reviews. This hybrid approach allowed them to capture both quantitative and descriptive evidence.

Restricting to Randomized Controlled Trials versus Including Observational Studies

Some umbrella reviews restrict inclusion to meta-analyses of randomized controlled trials because these provide the strongest evidence for causal inference. Other umbrella reviews include meta-analyses of observational studies when randomized trials are unavailable or when the research question concerns risk factors or harms that cannot be studied experimentally.

An umbrella review on the efficacy and safety of antidepressants in patients with comorbid depression and medical diseases included meta-analyses of placebo controlled or active controlled randomized clinical trials. The authors identified 176 systematic reviews in 43 medical diseases and included 52 meta-analyses in 27 medical diseases. This restriction to randomized trials strengthened the causal inferences that could be drawn.

Conducting a Meta-Analysis of Reviews versus Narrative Synthesis

Some umbrella reviews conduct a meta-analysis of the effect estimates reported in the included reviews. This approach provides a quantitative summary but requires that the included reviews report comparable effect estimates. Other umbrella reviews use narrative synthesis, which describes and compares the findings of included reviews without statistical pooling.

An umbrella review on the effects of aromatherapy on sleep quality planned to use appropriate statistical methods to summarize and describe the findings. The protocol noted that the efficacy of aromatherapy varies widely across studies, with some studies showing negligible or inconsistent effects. This variability makes quantitative synthesis challenging and may favor narrative synthesis.

Records and Measurements in Umbrella Reviews

Maintaining detailed records throughout the umbrella review process is essential for transparency and reproducibility. The following records should be maintained and made available as supplementary material.

Search Documentation

Document the search strategy for each database, including the search terms, filters, and date of search. Record the number of records retrieved from each database and the number of records identified through other sources such as reference list screening and hand searching. This documentation allows readers to assess the comprehensiveness of the search.

Screening Records

Maintain a record of the screening process, including the number of records screened at the title and abstract stage, the number of full texts retrieved, the number of full texts excluded, and the reasons for exclusion. This information is typically presented in a PRISMA flow diagram.

Data Extraction Forms

Maintain the data extraction forms used to capture information from each included review. These forms should be piloted on a sample of reviews and refined before full data extraction begins. Data extraction should be performed in duplicate by two independent reviewers to reduce errors.

An umbrella review on predicting falls in older adults completed data extraction in duplicate using a standardized spreadsheet and presented a narrative synthesis for each assessment tool. This approach ensured that data extraction errors were identified and corrected.

Quality Assessment Records

Maintain the quality assessment ratings for each included review, including the individual item ratings and the overall rating. These records allow readers to understand how the quality ratings were derived and to verify the accuracy of the assessments.

Common Failure Patterns in Umbrella Reviews

Researchers conducting umbrella reviews should be aware of common failure patterns that can compromise the validity of their findings.

Incomplete Search Strategies

A search strategy that misses relevant reviews can produce misleading conclusions. This failure often occurs when researchers search only one or two databases or when they fail to search for grey literature. The risk of incomplete searching is particularly high in fields where reviews are published in non-indexed journals or in languages other than English.

Inadequate Quality Assessment

Failing to assess the quality of included reviews is a critical error because low quality reviews can produce biased conclusions. Quality assessment should be performed using validated tools such as AMSTAR 2 or ROBIS, and the results should be reported transparently.

An umbrella review on irritable bowel syndrome risk factors found that most of the 69 included systematic reviews were of critically low quality, with the remaining reviews rated as low quality. Common shortcomings included the absence of a list of excluded studies with justifications for their exclusion and inadequate consideration of the risk of bias in individual studies. Without quality assessment, these limitations would have gone unnoticed.

Ignoring Overlap of Primary Studies

When multiple included reviews draw on the same primary studies, the evidence can be double counted. This can inflate the apparent strength of evidence and lead to overly confident conclusions. Researchers should quantify overlap using the corrected covered area and consider its impact on their findings.

Overinterpreting Weak Evidence

Umbrella reviews often find that the evidence base is weaker than individual reviews suggest. This occurs because quality assessment and evidence grading reveal limitations that are not apparent when reading a single review. Researchers should resist the temptation to overinterpret weak evidence and should clearly communicate the certainty of evidence to decision makers.

An umbrella review on the effects of maternal nutritional supplements and placental complications found evidence supporting supplementary vitamin D and or calcium, omega-3, multiple micronutrients, lipid based nutrients, and balanced protein energy in reducing the risks of adverse maternal and fetal health outcomes. However, the authors noted that these findings were limited by poor quality of evidence. This honest assessment of evidence quality is a hallmark of rigorous umbrella reviews.

Limitations of Umbrella Reviews

Umbrella reviews have several inherent limitations that researchers and readers should understand.

Dependence on the Quality of Included Reviews

An umbrella review cannot compensate for weaknesses in the included reviews. If the underlying systematic reviews and meta-analyses are of poor quality, the umbrella review will inherit those weaknesses. This is why quality assessment is such an important component of umbrella review methodology.

Risk of Overlap and Double Counting

When multiple included reviews draw on the same primary studies, the evidence can be double counted. This can inflate the apparent strength of evidence and lead to overly confident conclusions. Researchers should quantify overlap and consider its impact on their findings.

Publication and Reporting Bias

Systematic reviews and meta-analyses are subject to publication bias, meaning that reviews with positive or statistically significant findings may be more likely to be published than reviews with null findings. This bias can affect the conclusions of umbrella reviews.

An umbrella review on SGLT2 inhibitors in COVID-19 patients with type 2 diabetes mellitus found publication bias for hospitalization but not for mortality. The GRADE assessment indicated low to very low quality of evidence because of the observational studies included. This example illustrates how publication bias can affect specific outcomes within the same umbrella review.

Rapidly Evolving Evidence

In fast moving fields, the evidence base can change quickly. An umbrella review provides a snapshot of the evidence at a particular point in time, and its conclusions may become outdated as new reviews are published. Researchers should note the date of the literature search and consider whether an update is needed.

Safety and Regulatory Context

Umbrella reviews are not regulated as research studies in the same way as clinical trials, but they are subject to ethical and professional standards. Researchers should ensure that their umbrella review is conducted with the same rigor as a primary systematic review and that the findings are reported honestly and transparently.

The National Institute of Standards and Technology maintains the Research Data Framework, which provides guidance on managing research data throughout the research lifecycle. Researchers conducting umbrella reviews should follow best practices for data management, including documenting their search strategies, screening decisions, and data extraction forms.

The NC3Rs Experimental Design Assistant is a web based tool that helps researchers design rigorous and reproducible experiments. While this tool is primarily designed for primary research, the principles of rigorous experimental design apply equally to evidence synthesis. Researchers should consider how the design of their umbrella review could introduce bias and take steps to minimize these risks.

The National Center for Biotechnology Information provides access to a wide range of literature resources, including PubMed, which is a primary database for identifying systematic reviews and meta-analyses. The National Library of Medicine maintains PubMed as a free resource for searching the biomedical literature.

Professional Escalation Criteria

Researchers conducting umbrella reviews should know when to seek additional expertise or escalate concerns. The following situations warrant consultation with a methodologist, librarian, or statistician.

Uncertainty About Search Strategy

If you are unsure whether your search strategy will identify all relevant reviews, consult a health sciences librarian or information specialist. These professionals can help design and validate search strategies for systematic reviews and umbrella reviews.

Complex Statistical Analyses

If your umbrella review requires advanced statistical methods, such as meta-analysis of review level effect estimates or Bayesian sensitivity analysis, consult a statistician with experience in evidence synthesis. An umbrella review on SGLT2 inhibitors in COVID-19 used Bayesian sensitivity assessments to corroborate most of the findings, with differences observed in hospitalization and mortality outcomes.

Discrepant Findings Across Reviews

If the included reviews arrive at conflicting conclusions, consider whether the discrepancies can be explained by differences in inclusion criteria, search strategies, or statistical methods. If the discrepancies cannot be resolved, this should be reported as a finding of the umbrella review.

Evidence of Publication Bias

If your analysis suggests publication bias, consider whether the findings should be interpreted with additional caution. Publication bias can lead to overestimation of treatment effects or underestimation of harms.

Frequently Asked Questions

What is the difference between an umbrella review and a systematic review?

A systematic review identifies and synthesizes primary studies, such as randomized controlled trials or cohort studies, on a specific question. An umbrella review identifies and synthesizes systematic reviews and meta-analyses on a broader question. The unit of analysis in an umbrella review is the systematic review or meta-analysis itself, not the individual primary study.

When should I conduct an umbrella review instead of a systematic review?

Conduct an umbrella review when multiple systematic reviews or meta-analyses already exist on your topic and you want to compare their findings, assess their quality, and provide a consolidated summary for decision makers. Conduct a systematic review when you need to synthesize primary studies directly, either because no reviews exist or because you need to examine primary data in detail.

How do I search for systematic reviews and meta-analyses?

Search databases that index systematic reviews and meta-analyses, such as PubMed, Embase, Web of Science, the Cochrane Database of Systematic Reviews, and the Joanna Briggs Institute database. Use search filters for publication type and consider searching grey literature sources. Document your search strategy in enough detail that another researcher could reproduce it.

What quality assessment tools are used in umbrella reviews?

The most commonly used tools are AMSTAR 2, which stands for A Measurement Tool to Assess Systematic Reviews version 2, and ROBIS, which stands for Risk of Bias Assessment Tool for Systematic Reviews. Some umbrella reviews also apply GRADE, which stands for Grading of Recommendations Assessment, Development and Evaluation, to assess the certainty of evidence for each outcome.

How do I handle overlapping primary studies across included reviews?

Quantify overlap using the corrected covered area, or CCA, and consider using the GROOVE tool, which stands for Graphical Representation of Overlap of OVErviews, to visualize overlap. High overlap can inflate the apparent strength of evidence because the same primary studies are counted multiple times.

Can an umbrella review include narrative reviews?

Yes, some umbrella reviews include narrative reviews in addition to systematic reviews and meta-analyses. An umbrella review on predicting falls in older adults included narrative reviews and systematic reviews with or without meta-analyses. However, the inclusion criteria should be specified in advance and applied consistently.

How do I report an umbrella review?

Follow established reporting guidelines such as PRISMA, which stands for Preferred Reporting Items for Systematic Reviews and Meta-Analyses. The EQUATOR Network maintains a comprehensive collection of reporting guidelines for health research and can help you identify the appropriate guideline for your review type.

What are the main limitations of umbrella reviews?

Umbrella reviews depend on the quality of the included reviews, are subject to overlap and double counting of primary studies, and can be affected by publication and reporting bias. They also provide a snapshot of the evidence at a particular point in time and may become outdated as new reviews are published.

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References and Further Reading

• Research Data Framework. National Institute of Standards and Technology.
• EQUATOR Network. EQUATOR Network.
• Experimental Design Assistant. NC3Rs.
• NCBI Literature Resources. National Center for Biotechnology Information.
• PubMed. National Library of Medicine.
• Social media use and its impact on adolescent mental health: An umbrella review of the evidence.. Current opinion in psychology, 2022.
• Dietary sugar consumption and health: umbrella review.. BMJ (Clinical research ed.), 2023.
• Predicting falls in older adults: an umbrella review of instruments assessing gait, balance, and functional mobility.. BMC geriatrics, 2022.
• Risk factors for endometrial cancer: An umbrella review of the literature.. International journal of cancer, 2019.
• Efficacy and Safety of Antidepressants in Patients With Comorbid Depression and Medical Diseases: An Umbrella Systematic Review and Meta-Analysis.. JAMA psychiatry, 2023.
• Summarizing systematic reviews: methodological development, conduct and reporting of an umbrella review approach.. International journal of evidence-based healthcare, 2015.
• Health Effects of Various Edible Vegetable Oil: An Umbrella Review.. Advances in nutrition (Bethesda, Md.), 2024.
• Prehabilitation in adult patients undergoing surgery: an umbrella review of systematic reviews.. British journal of anaesthesia, 2022.
• SGLT2 Inhibitors in COVID-19: Umbrella Review, Meta-Analysis, and Bayesian Sensitivity Assessment.. 2025.
• SGLT2 Inhibitors in COVID-19: Umbrella Review, Meta-analysis, and Bayesian Sensitivity Assessment. 2024.
• Effects of Maternal Nutritional Supplements and Dietary Interventions on Placental Complications: An Umbrella Review, Meta-Analysis and Evidence Map.. 2021.
• Robot-assisted versus open kidney transplantation: an umbrella review of systematic reviews and meta-analyses.. 2026.
• Virtual reality for managing pain and fear and anxiety during pediatric needle procedures: an umbrella review.. 2026.
• Effectiveness of simulation technologies and virtual reality in enhancing empathy in health care education: an umbrella review.. 2026.
• Efficacy of psychological interventions for PTSD in distinct populations - An evidence map of meta-analyses using the umbrella review methodology.. Clinical Psychology Review, 2022.
• Effects of aromatherapy on sleep quality in patients: Protocol for an umbrella review. PLoS ONE, 2025.
• Global prevalence and contributing factors of nurse burnout: an umbrella review of systematic review and meta-analysis. BMC Nursing, 2025.
• Resilience of small and medium-sized enterprises in times of crisis: an umbrella review. Reviews of Management Sciences, 2025.
• Effectiveness of Irrigation Protocols in Endodontic Therapy: An Umbrella Review. Dental journal, 2025.
• Cadmium Exposure and Health Outcomes:An Umbrella Review of Meta-analyses.. Environmental Research, 2025.
• Risk factors for developing irritable bowel syndrome: systematic umbrella review of reviews. BMC Medicine, 2025.
• Use of Active Methodologies in Basic Education: An Umbrella Review. Education Sciences, 2025.
• The Path to Umbrella Reviews in Social Sciences. Exploring New Horizons. European Public and Social Innovation Review, 2025.

This article is educational and does not replace institutional policy, professional advice, or applicable safety and regulatory requirements.