Citation Contamination by Paper Mill Articles in Systematic Reviews of the Life Sciences

Systematic reviews are the criterion standard for evidence synthesis in the life sciences, yet their reliability and integrity are threatened by citation contamination from fabricated publications produced by paper mills. Despite growing awareness, the extent and implications of this issue remain unclear.

To analyze the prevalence, characteristics, affected subject areas, and citation patterns of retracted paper mill articles cited in systematic reviews.

This cross-sectional study analyzed systematic reviews published between 2013 and 2024, indexed in Web of Science (WoS). References were matched against the Retraction Watch dataset, and full texts were reviewed to identify retracted paper mill articles incorporated into the evidence synthesis.

The study assessed (1) contamination prevalence, defined as the proportion of systematic reviews incorporating retracted paper mill articles into the evidence synthesis; (2) geographic distribution of citing authors according to institutional affiliations; (3) citation timing and trends, including the time lag between incorporation and article retraction; (4) affected research areas, categorized by WoS subject classifications; and (5) citation patterns, including highly contaminated reviews (≥3 incorporations of retracted articles).

Of the total of 200 000 systematic reviews, 299 incorporated at least 1 retracted paper mill article into the evidence synthesis (contamination rate, 0.15%). Among them, 256 (85.6%) included a single retracted article, and 43 (14.4%) included multiple such articles. Of 1802 author affiliations associated with the contaminated reviews, 660 (36.6%) were from institutions in China. Of 385 total citations, 124 (32.2%) occurred after retraction, including 13 occurring more than 500 days after the retraction date. Oncology was the most affected field (48 of 299 [16.1%]). Five reviews each included 5 or more retracted articles, all published in journals under questionable publishers.

In this cross-sectional study of life sciences systematic reviews, contamination remained low but increased over time, posing a risk to research integrity. Continued citation of retracted articles, even after retraction, highlights the need for rigorous screening practices. Correcting contaminated reviews and developing automated detection tools are essential to preserving the credibility of systematic reviews.