Abstract
BACKGROUND: Prior epidemiological observational studies have duly documented a correlative link between inflammatory bowel disease (IBD) and bladder cancer (BC); however, the establishment of a definitive causal relationship has remained elusive. The principal objective of this meticulous investigation was to rigorously evaluate the causal nexus between IBD and BC, employing the robust methodology of Mendelian randomization (MR) analysis. METHODS: We meticulously performed both univariate and multivariate Mendelian randomization (MVMR) analyses employing publicly accessible genome-wide association study (GWAS) data. The central approach employed for our investigations was inverse variance weighting (IVW) method, while diligently scrutinizing potential sources of heterogeneity and horizontal pleiotropy via the rigorous utilization of Cochran's Q test, the MR-PRESSO method, and MR-Egger. RESULTS: In the univariate MR analysis, no causal link was observed between genetic prediction of IBD and BC. Furthermore, both Crohn's disease (CD) and ulcerative colitis (UC) showed no causal association with BC. The consistent association between CD and UC in the MVMR analysis supports this finding. CONCLUSION: This study found no genetic basis for the causative association of IBD and BC. It is crucial to emphasize that further comprehensive investigations are warranted to delve into the intricate underlying mechanisms that may contribute to these associations.