Since 1994, Cochrane has allowed the publication of certain systematic reviews to extend beyond the eponymous Database of Systematic Reviews and into the pages of a medical specialty journal with the hopes of increasing dissemination. Often, these copublished reviews will include an abridged version of the Cochrane review as well as commentary or other additional features explaining the review and its findings.
A new retrospective cohort study published in this month's issue of the Journal of Clinical Epidemiology highlights the benefits of such an approach. In brief, Zhu and colleagues investigated the rate of citation of Cochrane systematic reviews that had been copublished in a second journal versus those that were published only in the Database. Using a ratio of 2:1, the authors matched two randomly selected noncopublished reviews for each copublished review that came up in an indexed journal that had copublication agreements with Cochrane.
Out of the resulting sample of 101 copublished and 202 noncopublished reviews, the median number of citations over the first five years since publication was higher for reviews that had been copublished (71 versus 32.5, or approximately 118% higher in the copublished reviews). The median as higher for copublished reviews for the first, second, third, and fifth years specifically as well. In 19% of journals, the copublication of a review led to a subsequent increase in impact factor over the following year; this was true for 27.3% of journals during the second year. There was no clear trend over time for the rate of copublication across journals, though the total number of Cochrane reviews published during the same period generally increased.
Zhu, L., Zhang, Y., Yang, R., et al. (2022). Copublication improved the dissemination of Cochrane reviews and benefited copublishing journals: A retrospective cohort study. J Clin Epidemiol 149:110-117. Manuscript available at publisher's website here.