Irritable Bowel Syndrome and Long-Term Risk of Cancer: A Prospective Cohort Study Among 0.5 Million Adults in UK Biobank

To investigate the prospective association of irritable bowel syndrome (IBS) with long-term risk of overall, site-specific cancer and cancer-specific mortality in general population.Participants free of inflammatory bowel disease, celiac disease, and any cancer at baseline from the UK Biobank were included, with patients with IBS as the exposure group and non-IBS patients as the reference group. The primary outcome was the incidence of overall cancer and cancer-specific mortality. Secondary outcomes included site-specific cancers and types of digestive cancers. The Cox proportional hazard model was used to investigate the associated risk of incident malignancies and related mortality.Among 449,595 participants, 22,338 (5.0%) were diagnosed with IBS. During a median of 12.2-year follow-up, 2,937 cases of incident cancer were identified in patients with IBS (11.47 per 1,000 person-years), compared with 60,556 cases in reference individuals (12.51 per 1,000 person-years). Of these cases, 512 and 12,282 cancer-specific deaths occurred in IBS and non-IBS groups. Compared with non-IBS, the adjusted hazard ratio for overall cancer and cancer-specific mortality was 0.97 (95% confidence interval: 0.93-1.00, P = 0.062) and 0.83 (0.76-0.91, P < 0.001) among patients with IBS. Specifically, decreased risk of digestive (0.79 [0.71-0.89]), particularly colon (0.75 [0.62-0.90]) and rectal (0.68 [0.49-0.93]), cancers was observed in patients with IBS. Further sensitivity analysis and subgroup analysis by age and sex indicated similar results.Compared with the general population, IBS does not increase the overall risk of cancer. Conversely, IBS is associated with lower risk of incident colorectal cancer and cancer-specific mortality.