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

Introduction 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. Methods Participants free of inflammatory bowel disease, coeliac disease and any cancer at baseline from the UK Biobank were included, with IBS patients as exposure group and non-IBS patients as reference group. Primary outcome was the incidence of overall cancer and cancer specific mortality. Secondary outcomes included site-specific cancers and types of digestive cancers. Cox proportional hazard model was used to investigate the associated risk of incident malignancies and related mortality. Results Among 449,595 participants, 22338(5.0%) were diagnosed with IBS. During a median of 12.2-year follow-up, 2937 cases of incident cancer were identified in IBS patients (11.47 per 1000 person-years), compared with 60,556 cases in reference individuals (12.51 per 1000 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%CI: 0.93-1.00, P=0.062) and 0.83 (0.76-0.91, P<0.001) among IBS patients. 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 were observed in IBS patients. Further sensitivity analysis and subgroup analysis by age and gender indicated similar results. Discussion 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.