The Journal Impact Factor has long been the default metric for evaluating research quality, but a new analysis of nearly 4,000 articles in sleep medicine reveals that it tells researchers almost nothing about how an individual paper will perform.
A team led by Salman Hussain (University of Ottawa, McGill University, Stanford University, and the University of Toronto) examined citation distributions in the top 10 sleep science journals. Their study, published in Sleep and Breathing, found that citation patterns are so heavily skewed that the JIF explains only about 4.4% of the variance in how often individual articles are cited.
What They Found
The researchers analyzed 3,949 original and review articles published in 2020 and 2021 across the top 10 sleep medicine journals, tracking all citations received in 2022. The picture that emerged is one of extreme inequality:
- 16.0% of articles received zero citations in 2022
- 18.7% received exactly one citation
- Only 27.7% of articles were cited more often than their journal’s JIF would suggest
- 72.3% fell below their journal’s JIF
- 12.5% of articles accounted for 50% of all citations
- Review articles consistently outperformed original research in citation counts
The correlation between citation rate and JIF was statistically significant (r = 0.21, p < 0.001) but practically meaningless, the JIF predicted less than 5% of the variation in individual article performance.
Why It Matters
The finding has direct implications for how research is evaluated. University promotion committees, grant reviewers, and hiring panels frequently use JIF as a proxy for the quality of a researcher’s individual papers. This study demonstrates that such reliance is misplaced in sleep medicine.
“Citation distributions in leading sleep journals are highly skewed, and journal impact factor has limited utility for predicting individual article influence,” the authors write. They recommend instead that evaluators use article-level indicators, such as actual citation counts, altmetrics, and qualitative appraisal, rather than assuming that publication in a high-JIF journal guarantees high impact.
The study also raises questions about the “publish or perish” culture. With nearly one in five sleep medicine papers receiving zero citations in their first full year, the pressure to publish in high-impact journals may not translate into genuine scholarly engagement with the work.
Limits
The study examined a single citation year (2022) within a single discipline. Self-citations and citation network effects were not analyzed. The analysis was limited to the top 10 journals by JIF, which may not reflect patterns across smaller or more specialized sleep journals. Future work incorporating multiple JIF cycles and broader journal sets would strengthen the conclusions.
Bottom Line
In sleep medicine, a journal’s impact factor is a poor predictor of any individual article’s reach. Evaluators should look at the paper, not the journal.
Source
Salman Hussain et al. “Beyond impact factor: citation skew and article-level influence in sleep medicine journals.” Sleep and Breathing, 2026 Jun 20;30(4):193. DOI: 10.1007/s11325-026-03735-7. PMID: 42322369.