Inflated numbers of authors over time have not been just due to increasing research complexity

J Clin Epidemiol. 2008 Jun;61(6):546-51. doi: 10.1016/j.jclinepi.2007.07.017. Epub 2008 Mar 10.


Objective: To examine trends in and determinants of the number of authors in clinical studies.

Study design and setting: We analyzed determinants of the number of authors in 633 articles of randomized trials and 313 articles of nonrandomized studies included in large meta-analyses (seven and six topics, respectively). Analyses were adjusted for topic. We also evaluated 310 randomly sampled case reports that had an abstract and described a single case.

Results: After adjusting for topic and other determinants, for both randomized trials and nonrandomized studies, the number of authors increased by 0.8 per decade (P<0.001). Topic was a strong determinant of the number of authors; other independent factors included journal impact factor, multinational authorship, and (for randomized trials) article length and sample size. Trials from South Europe (+1.1 authors) and North America (+0.9) and nonrandomized studies from South Europe (+1.8) had more authors than studies from North Europe (P<0.001). For case reports, only geographic location and article length were significantly related with author numbers.

Conclusion: The number of authors in articles of randomized and nonrandomized studies has increased over time, even after adjusting for the topic, size, and visibility of a study. The academic coinage of authorship may be suffering from inflation.

MeSH terms

  • Authorship*
  • Bibliometrics
  • Biomedical Research / trends*
  • Humans
  • Medical Records / statistics & numerical data
  • Periodicals as Topic / statistics & numerical data
  • Periodicals as Topic / trends
  • Publishing / statistics & numerical data
  • Publishing / trends
  • Randomized Controlled Trials as Topic / statistics & numerical data
  • Randomized Controlled Trials as Topic / trends