Title: Increasing number of authors in Cochrane reviews
To investigate authorship trends in Cochrane reviews; both overall and within each of the editorial groups; and to examine if the authorship criteria from the International Committee of Medical Journal Editors (ICMJE) were met for Cochrane reviews with more than 15 authors based on the text in the section “Contributions of authors”.
We included Cochrane reviews from 1996 to 2018.
We included a total of 7,447 Cochrane reviews. The median number of authors per Cochrane review was 3 in 1996 (IQR 2-3, range 2-3), 4 in 2007 (IQR 3-5, range 1-13), and 5 in 2018 (IQR 4-7, range 2-22). Within each of the 55 editorial groups, the total number of authors either increased (47%) or was unchanged (53%). A total of 27 Cochrane reviews had more than 15 authors. Based on the text in “Contributions of authors”, 59% (16/27) of the reviews with more than 15 authors had authors that did not fulfill the ICMJE authorship criteria. However, the text in “Contributions of authors” was often difficult to interpret.
The number of authors per Cochrane review gradually increased from 1996 to 2018. The ICMJE authorship criteria were most likely not met by all authors in more than half of the reviews with more than 15 authors.