Numbers and Trends in Authorship of Published Meta-analyses, 1990-2019

Marios Papadakis1


The aim of this study was to investigate the evolution of authorship trends in MEDLINE-indexed meta-analyses over time. Although similar studies do exist,1 they all have major limitations (cross-sectional nature, small sample sizes, etc) that do not allow for reliable conclusions to be drawn. This may be the first work to study authorship patterns in all MEDLINE-indexed meta-analyses published.


In PubMed, the search filters of study type and publication date were applied, and the search was restricted to meta-analyses published until December 31, 2019. Single research group names included in the article’s title were considered equivalent to 1 coauthor. Articles without author names were excluded from the study.


A total of 116,710 meta-analyses were analyzed. The most meta-analyses per year were published in 2019 (1.2%), followed by 2018 (1.1%). The overall mean (SD) number of authors was 5.4 (4). The most common number of authors was 4, found in 16.4% of articles, followed by 5 authors (15.4%). The mean number of authors per article increased significantly over time, from 3 in 1990-1994 to 5.8 in 2015-2019. Single-author articles represented 24% of all articles in 1990-1994 and only 1.2% in 2015-2019. The number of articles authored by 15 or more authors increased from 0% in 1990-1994 to 3.2% in 2015-2019.


The reported trend of authorship proliferation1,2 was also observed in meta-analyses, with a current mean number of 5.8 authors per article. It is doubtful whether this increase can only be attributed to increasing research complexity.2 Scientists should adhere to the existing guidelines and include in the author list only contributors who qualify for inclusion. Journals should adopt more strict policies to confirm that only substantial contributions are getting credited with authorship.


1. Gülen S, Fonnes S, Andresen K, Rosenberg J. Increasing number of authors in Cochrane reviews. J Evid Based Med. 2020;13(1):34-41. doi:10.1111/jebm.12371

2. Papatheodorou SI, Trikalinos TA, Ioannidis JPA. Inflated numbers of authors over time have not been just due to increasing research complexity. J Clin Epidemiol. 2008;61(6):546-551. doi:10.1016/j.jclinepi.2007.07.017

1Department of Surgery II, University Witten-Herdecke, Witten, Germany, marios_papadakis@yahoo.gr

Conflict of Interest Disclosures

None reported.