Global mapping of overviews of systematic reviews in healthcare published between 2000 and 2020: a bibliometric analysis.

OBJECTIVE: To conduct a bibliometric analysis using a large sample of overviews of systematic reviews (OoSRs) and reveal research trends and areas of interest about these studies. STUDY DESIGN AND SETTING: We searched MEDLINE, Scopus and Cochrane Database of Systematic Reviews from 1/1/2000 to 15/10/2020. We used Scopus meta-data and two authors recorded supplementary information independently. We summarized the data using frequencies with percentages. RESULTS: A total of 1558 studies were considered eligible for analysis. We found that the publications have been increasing yearly and their nomenclature was not uniform (the most frequent label in the title was "overview of systematic reviews"). The largest number of papers and the most cited ones were published by corresponding authors from the UK. The publications were distributed across 737 scholarly journals and many of them were published in the field of complementary/alternative medicine, psychiatry/psychology, nutrition/dietetics, and pediatrics. The co-authorship analysis revealed collaborations among countries. The most common clinical conditions were depression, diabetes, cancer, dementia, pain, cardiovascular disease, stroke, obesity, and schizophrenia. CONCLUSION: OoSRs have recently become a popular approach of evidence synthesis. International collaborations between overview authors from countries with increased research productivity and countries with less research activity should be encouraged.

Methods for depicting overlap in overviews of systematic reviews: An introduction to static tabular and graphical displays.

BACKGROUND AND OBJECTIVE: To introduce potential static tabular and graphical techniques for visually presenting overlap between systematic reviews (SRs) included in overviews of systematic reviews (OoSRs). METHODS: The graphical approaches described include Venn and Euler diagrams, as well as matrix-based, node-link, and aggregation-based techniques. We used fundamental concepts of mathematics from set and network theory to develop our novel graphical approaches. The graphical displays were created using R. RESULTS: Overview authors have the flexibility to choose from a variety of visualizations, depending on the characteristics of their study. If the OoSRs include few SRs, a Venn or an Euler diagram can be used. In case of OoSRs with more SRs, Upset plots, heatmaps, and node-link graphs are more appropriate for visualizing overlapping SRs. Stacked bar plots constitute an aggregation-based technique of illustrating overlap. Strengths and limitations of each graphical approach are presented. CONCLUSION: The degree of overlap should be explored for the entire study and for specific outcomes of interest. The proposed graphical techniques may assist methodologists and authors in identifying overlap, which in turn may improve validity and transparency in OoSRs. More research is needed to understand which technique would be most useful and easiest to understand.