Bibliometric study of ‘overviews of systematic reviews’ of health interventions: evaluation of prevalence, citation and impact factor

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.