Overviews synthesising the results of multiple systematic reviews help inform evidence‐based clinical practice. In this first of two companion papers, we evaluate the bibliometrics of overviews, including their prevalence and factors affecting citation rates and journal impact factor (JIF). We searched MEDLINE, Epistemonikos and Cochrane Database of Systematic Reviews (CDSR). We included overviews that: (a) synthesised reviews, (b) conducted a systematic search, (c) had a methods section and (d) examined a healthcare intervention. Multivariable regression was conducted to determine the association between citation density, JIF and six predictor variables. We found 1218 overviews published from 2000 to 2020; the majority (73%) were published in the most recent 5‐year period. We extracted a selection of these overviews (n = 541; 44%) dated from 2000 to 2018. The 541 overviews were published in 307 journals; CDSR (8%), PLOS ONE (3%) and Sao Paulo Medical Journal (2%) were the most prevalent. The majority (70%) were published in journals with impact factors between 0.05 and 3.97. We found a mean citation count of 10 overviews per year, published in journals with a mean JIF of 4.4. In multivariable analysis, overviews with a high number of citations and JIFs had more authors, larger sample sizes, were open access and reported the funding source. An eightfold increase in the number of overviews was found between 2009 and 2020. We identified 332 overviews published in 2020, which is equivalent to one overview published per day. Overviews perform above average for the journals in which they publish.

BackgroundMultiple 'overviews of reviews' conducted on the same topic ("overlapping overviews") represent a waste of research resources and can confuse clinicians making decisions amongst competing treatments. We aimed to assess the frequency and characteristics of overlapping overviews. MethodsMEDLINE, Epistemonikos and Cochrane Database of Systematic Reviews were searched for overviews that: synthesised reviews of health interventions and conducted systematic searches. Overlap was de ned as: duplication of PICO eligibility criteria, and not reported as an update nor a replication. We categorized overview topics according to 22 WHO ICD-10 medical classi cations, overviews as broad or narrow in scope, and overlap as identical, nearly identical, partial, or subsumed. Subsummation was de ned as when broad overviews subsumed the populations, interventions and at least one outcome of another overview. ResultsOf 541 overviews included, 169 (31%) overlapped across similar PICO, fell within 13 WHO ICD-10 medical classi cations, and 62 topics. 148/169 (88%) overlapping overviews were broad in scope. Fifteen overviews were classi ed as having nearly identical overlap (9%); 123 partial overlap (73%), and 31 subsumed (18%) others. ConclusionsOne third of overviews overlapped in content and a majority covered broad topic areas. A multiplicity of overviews on the same topic adds to the ongoing waste of research resources, time and effort across medical disciplines. Authors of overviews can use this study and the sample of overviews to identify gaps in the evidence for future analysis, and topics that are already studied which do not need to be duplicated. HighlightsThis is the rst study to examine overlap across a sample of overviews of reviews.Of 541 overviews published from 2000 to 2018, 169 (31%) were considered overlapping in topic with one or more overviews.

Background: Overviews synthesizing the results of multiple systematic reviews help inform evidence-based clinical practice. In this first of two companion papers, we evaluate the bibliometrics of ‘overviews of systematic reviews’, including their prevalence, number of citations, and factors affecting citation rates and journal impact factor.Methods: We searched MEDLINE, Epistemonikos and the Cochrane library databases. We applied eligibility criteria to identify overviews that: (a) aimed to focus on synthesizing reviews, (b) conducted a systematic search, (c) had a full methods section, and (d) examined a health intervention or clinical treatment effect. A multivariate regression was conducted to determine the association between citation density and impact factor and 6 predictor variables of interest. Results: We found 1218 overviews published from 2000 to 2020; the majority (73%) of which were published in the most recent 5-year period (2016-2020). We extracted a selection of these overviews (n=541; 44%) dated from 2000 to 2018. The 541 overviews were published in 307 journals; the Cochrane Database of Systematic Reviews (8%), PLOS ONE (3%) and the Sao Paulo Medical Journal (2%) being the most prevalent. The majority of overviews (70%) were published in journals with impact factors between 0.05 and 3.97. The average citation rate was 90 (SD ±219.7) over 9 years, or 10 citations per overview per year. In multivariate analysis, overviews with a high number of citations and high journal impact factors tended to have more authors, larger sample sizes, be open access and report funding source. Conclusions: We found an 8 fold increase in the number of overviews from 2009 to 2020; and a representation of one published a day in 2020. Factors driving the increase in overviews include the exponential increase in the number of systematic reviews, the publication of Cochrane guidance on overview of reviews in 2009 and the subsequent publication of the first Cochrane overview in the same year. Our study found a significantly higher mean citation count of 10 overviews per year, published in journals with a mean impact factor of 4.4. These data indicate that, overall, overviews perform above average for the journals in which they publish. We also found that highly cited overviews in high impact factor journals had group authorship, large sample sizes, were openly accessible, and reported funding source.

Background Multiple ‘overviews of reviews’ conducted on the same topic (“overlapping overviews”) represent a waste of research resources and can confuse clinicians making decisions amongst competing treatments. We aimed to assess the frequency and characteristics of overlapping overviews. Methods MEDLINE, Epistemonikos and Cochrane Database of Systematic Reviews were searched for overviews that: synthesised reviews of health interventions and conducted systematic searches. Overlap was defined as: duplication of PICO eligibility criteria, and not reported as an update nor a replication. We categorized overview topics according to 22 WHO ICD-10 medical classifications, overviews as broad or narrow in scope, and overlap as identical, nearly identical, partial, or subsumed. Subsummation was defined as when broad overviews subsumed the populations, interventions and at least one outcome of another overview. Results Of 541 overviews included, 169 (31%) overlapped across similar PICO, fell within 13 WHO ICD-10 medical classifications, and 62 topics. 148/169 (88%) overlapping overviews were broad in scope. Fifteen overviews were classified as having nearly identical overlap (9%); 123 partial overlap (73%), and 31 subsumed (18%) others. Conclusions One third of overviews overlapped in content and a majority covered broad topic areas. A multiplicity of overviews on the same topic adds to the ongoing waste of research resources, time and effort across medical disciplines. Authors of overviews can use this study and the sample of overviews to identify gaps in the evidence for future analysis, and topics that are already studied which do not need to be duplicated.

Background: Overviews synthesising the results of multiple systematic reviews help inform evidence-based clinical practice. In this first of two companion papers, we evaluate the bibliometrics of overviews, including their prevalence and factors affecting citation rates and JIF (JIF).Methods: We searched MEDLINE, Epistemonikos and Cochrane Database of Systematic Reviews (CDSR). We included overviews that: (a) synthesised reviews, (b) conducted a systematic search, (c) had a methods section, and (d) examined a healthcare intervention. Multivariable regression was conducted to determine the association between citation density, JIF and 6 predictor variables. Results: We found 1218 overviews published from 2000 to 2020; the majority (73%) were published in the most recent 5-year period. We extracted a selection of these overviews (n=541; 44%) dated from 2000 to 2018. The 541 overviews were published in 307 journals; CDSR (8%), PLOS ONE (3%) and Sao Paulo Medical Journal (2%) were the most prevalent. The majority (70%) were published in journals with impact factors between 0.05 and 3.97. We found a mean citation count of 10 overviews per year, published in journals with a mean JIF of 4.4. In multivariable analysis, overviews with a high number of citations and JIFs had more authors, larger sample sizes, were open access and reported the funding source. Conclusions: An 8-fold increase in the number of overviews was found between 2009 and 2020. We identified 332 overviews published in 2020, which is equivalent to 1 overview published per day. Overviews perform above average for the journals in which they publish.

Background Multiple overviews of systematic reviews conducted on the same topic (“overlapping overviews”) represent a waste of research resources and can confuse or mislead clinicians and policymakers. We aimed to assess the frequency and characteristics of published overviews addressing the same clinical question or topic. Methods We used MEDLINE, Epistemonikos and Cochrane databases to locate overviews that: focused on synthesising reviews; conducted systematic searches; had a methods section; and examined a health intervention or clinical treatment. We then determined which overviews addressed the same or overlapping populations/settings, interventions, and outcomes [PIO]). Overlap in topic was defined as: duplication of PIO elements, not representing an update of a previous overview, and not a replication for quality purposes. Results Of 541 overviews located (2000–2018), 178 (33%) overlapped with another overview addressing a similar PIO. The topics of overlapping overviews fell within 13 WHO ICD-10 medical classifications, and there were 65 overlapping topics in total. The most prevalent topic with overlap across 7 overviews was smoking cessation (pharmacologic and non-pharmacologic interventions). Five overlapping overviews related to acupuncture for pain, 5 addressed cannabinoids for pain and symptoms, and 5 addressed exercise for bone and muscle health. For 15/65 (22%) of these topics, one author was involved in at least two of the overlapping overviews. Conclusions We found significant duplication and unnecessary overlap across overviews. To avoid waste and redundancy, protocols of overviews should be registered in a targeted database, and overviews should cite other studies on similar topic with a rationale.

Background: Overviews synthesising the results of multiple systematic reviews help inform evidence-based clinical practice. In this first of two companion papers, we evaluate the bibliometrics of overviews, including their prevalence and factors affecting citation rates and journal impact factor.Methods: We searched MEDLINE, Epistemonikos and Cochrane databases. We included overviews that: (a) synthesised reviews, (b) conducted a systematic search, (c) had a methods section, and (d) examined a healthcare intervention. Multivariate regression was conducted to determine the association between citation density, impact factor and 6 predictor variables. Results: We found 1218 overviews published from 2000 to 2020; the majority (73%) were published in the most recent 5-year period. We extracted a selection of these overviews (n=541; 44%) dated from 2000 to 2018. The 541 overviews were published in 307 journals; Cochrane Database (8%), PLOS ONE (3%) and Sao Paulo Medical Journal (2%) were the most prevalent. The majority (70%) were published in journals with impact factors between 0.05 and 3.97. We found a mean citation count of 10 overviews per year, published in journals with a mean impact factor of 4.4. In multivariate analysis, overviews with a high number of citations and impact factors had more authors, larger sample sizes, were open access and reported the funding source. Conclusions: An 8-fold increase in the number of overviews was found between 2009 and 2020. We identified 332 overviews published in 2020, which is equivalent to 1 overview published per day. Overviews perform above average for the journals in which they publish.

Background Multiple ‘overviews of reviews’ conducted on the same topic (“overlapping overviews”) represent a waste of research resources and can confuse clinicians making decisions amongst competing treatments. We aimed to assess the frequency and characteristics of overlapping overviews. Methods MEDLINE, Epistemonikos and Cochrane Database of Systematic Reviews were searched for overviews that: synthesised reviews of health interventions and conducted systematic searches. Overlap was defined as: duplication of PICO eligibility criteria, and not reported as an update nor a replication. We categorized overview topics according to 22 WHO ICD-10 medical classifications, overviews as broad or narrow in scope, and overlap as identical, nearly identical, partial, or subsumed. Subsummation was defined as when broad overviews subsumed the populations, interventions and at least one outcome of another overview. Results Of 541 overviews included, 169 (31%) overlapped across similar PICO, fell within 13 WHO ICD-10 medical classifications, and 62 topics. 148/169 (88%) overlapping overviews were broad in scope. Fifteen overviews were classified as having nearly identical overlap (9%); 123 partial overlap (73%), and 31 subsumed (18%) others. Conclusions One third of overviews overlapped in content and a majority covered broad topic areas. A multiplicity of overviews on the same topic adds to the ongoing waste of research resources, time and effort across medical disciplines. Authors of overviews can use this study and the sample of overviews to identify gaps in the evidence for future analysis, and topics that are already studied which do not need to be duplicated.