Aim: Cochrane reviews are internationally recognized for their high quality, but to reduce the risk of transmitting misleading information, they must be kept up to date. The aim of this study was to quantify the number of reviews in the Cochrane Database of Systematic Reviews (CDSR) that have not been updated for more than five years and to characterize them.
Method: This study was reported closely adapted to the STROBE guidelines. Information about all reviews in the CDSR was extracted in August 2020. Based on a previous study, we defined inactive reviews as reviews with no update in "What's New" or no publication of a new version of the review within the last 5.5 years. The inactive reviews were quantified and characterized and results were visualized through tables and charts.
Results: The study included 7931 reviews from the CDSR. The median age of all reviews in the CDSR was 5.3 years. Fifty-five percent were published for the first time between 1996 and February 2015 and 88% of these had been inactive for 5.5 years or more. Among these, 89% were first publication of the review that had never been updated afterward.
Conclusion: More than half of the Cochrane reviews in CDSR were first published before 2015 and only 12% of these were still active. In order to retain their validity, it would be preferable if Cochrane reviews were kept up to date by the authors either by an update in "What's New" or by publishing a new version of the review.
Keywords: Cochrane; evidence-based medicine; methodology; out of date; reporting; systematic reviews; update.
© 2021 Chinese Cochrane Center, West China Hospital of Sichuan University and John Wiley & Sons Australia, Ltd.