Meta-analyses neglect previous systematic reviews and meta-analyses about the same topic

Article type
Authors
Helfer B1, Prosser A2, Samara M1, Geddes J3, Cipriani A3, Davis J4, Mavridis D5, Salanti G5, Leucht S1
1Cochrane Schizophrenia Group, Germany
2Centre for Addiction and Mental Health, Toronto, Canada
3University of Oxford, United Kingdom
4Cochrane Schizophrenia Group, USA
5Cochrane Statistical Method Group, Greece
Abstract
The following abstract is a part of an article accepted for publication in BMC Medicine.

Background: As the number of systematic reviews is growing rapidly, we investigate systematically whether meta-analyses published in leading medical journals present an outline of available evidence by referring to previous meta-analyses and systematic reviews.
Methods: We 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 influenced the referencing practices.
Results: We 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 (OR) 1.49; 95% confidence interval (CI) 1.06 to 2.10) and more recent publication year (OR 1.19; 95% CI 1.034 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 (OR 0.38; 95% CI 0.17 to 0.88), and the probability of being discussed was increased for previous studies that employed meta-analytic methods (OR 32.36; 95% CI 2.00 to 522.85).
Conclusions: Meta-analyses on pharmacological treatments do not consistently refer to or 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.