Background <p>Research misconduct poses a significant threat to the integrity of evidence synthesis. Although Cochrane reviews are known for rigorous methodological standards, the potential inclusion of studies authored by researchers with substantial retractions records raises concerns about the reliability of their conclusions.</p> Objectives <p>This study aims to (a) quantify the extent to which Cochrane reviews include or cite papers authored by researchers with at least 24 retractions (as listed in the Retraction Watch Leaderboard),and (b) examine whether sensitivity analyses were performed and identify the stated reasons for excluding those studies from the reviews.</p> Methods <p>The Retraction Watch database was used to identify researchers with 24 or more retractions in the database. This was done with custom code in Stata, created to identify individuals with &gt; 24 entries. Data on Cochrane’s systematic reviews that included or referenced the studies by authors with 24 or more retraction records was collected. For reviews where these studies were excluded, the stated reasons for exclusion were recorded. We also assessed the frequency and nature of sensitivity analyses conducted to account for potential bias from problematic studies.</p> Results <p>Of 9,323 Cochrane Reviews, 81(0.9%)included or cited at least one potentially fraudulent study. 57(0.6%) of these reviews referenced and 32(0.3%) included such studies in meta-analyses. In cases where such studies were excluded, the justification was typically unrelated to trustworthiness. Of the 32 reviews that include potentially fraudulent studies, only a minority of reviews (19%, 6 out of 32) conducted sensitivity analyses after paper exclusions, primarily due to retracted papers, with only one analysis conducted in response to potential fraudulent studies.</p> Conclusion <p>The inclusion or insufficient handling of studies by highly retracted researchers in Cochrane reviews without sensitivity analysis highlights the concerns regarding the integrity and reliability of evidence used to guide clinical practice. This study underscores the need for formal mechanisms to assess author trustworthiness, recommends transparency in handling these studies, and calls for sensitivity analyses to be mandatory.</p>