Abstract
BackgroundAs the number of systematic reviews is growing rapidly, we systematically investigate whether meta-analyses published in leading medical journals present an outline of available evidence by referring to previous meta-analyses and systematic reviews.MethodsWe searched PubMed for recent meta-analyses of pharmacological treatments published in high impact factor journals. Previous systematic reviews and meta-analyses were identified with electronic searches of keywords and by searching reference sections. We analyzed the number of meta-analyses and systematic reviews that were cited, described and discussed in each recent meta-analysis. Moreover, we investigated publication characteristics that potentially influence the referencing practices.ResultsWe identified 52 recent meta-analyses and 242 previous meta-analyses on the same topics. Of these, 66% of identified previous meta-analyses were cited, 36% described, and only 20% discussed by recent meta-analyses. The probability of citing a previous meta-analysis was positively associated with its publication in a journal with a higher impact factor (odds ratio, 1.49; 95% confidence interval, 1.06 to 2.10) and more recent publication year (odds ratio, 1.19; 95% confidence interval 1.03 to 1.37). Additionally, the probability of a previous study being described by the recent meta-analysis was inversely associated with the concordance of results (odds ratio, 0.38; 95% confidence interval, 0.17 to 0.88), and the probability of being discussed was increased for previous studies that employed meta-analytic methods (odds ratio, 32.36; 95% confidence interval, 2.00 to 522.85).ConclusionsMeta-analyses on pharmacological treatments do not consistently refer to and discuss findings of previous meta-analyses on the same topic. Such neglect can lead to research waste and be confusing for readers. Journals should make the discussion of related meta-analyses mandatory.Electronic supplementary materialThe online version of this article (doi:10.1186/s12916-015-0317-4) contains supplementary material, which is available to authorized users.
Highlights
As the number of systematic reviews is growing rapidly, we systematically investigate whether meta-analyses published in leading medical journals present an outline of available evidence by referring to previous meta-analyses and systematic reviews
The number of systematic reviews is growing rapidly in 2010 approximately 11 such studies were published per day, which corresponds to the number of randomized controlled trials (RCTs) published three decades ago [2]
Germany Full list of author information is available at the end of the article. Because of this exponential growth in publication rates, many meta-analysis authors may not discuss the results of previous meta-analyses and systematic reviews on the same topic - in a manner analogous to authors of RCTs not referring to a substantial portion of other relevant RCTs [3] or systematic reviews [4,5]
Summary
As the number of systematic reviews is growing rapidly, we systematically investigate whether meta-analyses published in leading medical journals present an outline of available evidence by referring to previous meta-analyses and systematic reviews. The number of systematic reviews is growing rapidly in 2010 approximately 11 such studies were published per day, which corresponds to the number of randomized controlled trials (RCTs) published three decades ago [2] Because of this exponential growth in publication rates, many meta-analysis authors may not discuss the results of previous meta-analyses and systematic reviews on the same topic - in a manner analogous to authors of RCTs not referring to a substantial portion of other relevant RCTs [3] or systematic reviews [4,5]. Not referring to important related research is against the principles of evidence-based medicine, because meta-analysts agree that all available evidence should be systematically searched and reviewed in an unbiased manner [12]
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