An evaluation of impact factor bias of clinical trials published in pain journals

Studies with nonsignificant results are less likely to be published or published in lower impact factor journals. To determine whether a similar phenomenon occurs in pain literature, we explored impact factor bias in peer-reviewed pain journals.

A PubMed search involving randomized controlled trials in pain journals during 2012 through 2018 was performed. The primary outcome was the publication impact factor. Exclusion criteria included commentaries, editorials, meta-analyses, reviews, and animal studies. The average impact factor for each journal was determined. The primary independent variable was a study with a positive outcome.

Of the 9 journals evaluated, 1108 articles met our inclusion criteria and were included in our analysis. The quartiles for the impact factor for the journals included were 2.5, 2.9, and 3.6. A multivariate analysis identified sample size greater than 100, description of a sample size calculation, presence of a stated hypothesis, and presence of sponsorship funding as independent predictors of publication in a journal with greater impact factor. In contrast, positive results were not associated with publication in a greater impact factor journal, even when forced into the model, P = 0.49.

After adjusting for study factors associated with publication, there is no evidence of impact factor bias within the pain literature. The lack of impact factor bias in the pain literature is a positive finding for the field and should benefit scientific development and the clinical care of patients.