The causality between chronic rhinosinusitis and inflammatory bowel disease: A bidirectional 2-sample Mendelian randomization analysis

Prior observational studies suggested an association between chronic rhinosinusitis (CRS) and inflammatory bowel disease (IBD), but causality remains unclear. This study employed a bidirectional 2-sample Mendelian randomization (MR) analysis to investigate potential causal relationships. Genetic variants associated with CRS and IBD (including Crohn’s disease and ulcerative colitis) were sourced from the IEU Open genome-wide association study project. Primary analysis used inverse-variance weighted, supplemented by weighted median and MR-Egger methods. Sensitivity analyses included Cochran’s Q test, MR-Egger intercept, Mendelian Randomization Pleiotropy RESidual Sum and Outlier, and leave-one-out analysis. Inverse-variance weighted revealed CRS increased IBD risk (OR = 1.108, 95% confidence interval = 1.009–1.217, P = .032), while reverse MR indicated IBD increased CRS risk (OR = 1.035, 95% confidence interval = 1.001–1.071, P = .043). No significant causality was found between CRS and IBD subtypes, Crohn’s disease and ulcerative colitis. Sensitivity analyses supported robustness, with no evidence of pleiotropy ( P > .05). This MR study suggests a bidirectional causal relationship between CRS and IBD, though not with subtypes. Further research is needed to elucidate underlying mechanisms.