Association between irritable bowel syndrome and colorectal cancer: A nationwide population-based study

• IBS was not associated with the long-term development of CRC.
• IBS cohort underwent more colonoscopies/sigmoidoscopies than non-IBS cohort.
• Increased CRC risk may be initially misclassified as IBS in the first 2 years.

ObjectivesTo determine whether irritable bowel syndrome (IBS) is associated with an increased risk for the subsequent colorectal cancer (CRC).MethodsWe identified 91,746 patients who were diagnosed with IBS between 2000 and 2010 from the Taiwan National Health Insurance Research Database (NHIRD) as the study cohort, and randomly extracted the data of 183,492 patients matched by sex, age, and baseline year for the comparison cohort. The follow-up period was terminated after CRC development, withdrawal from the national health insurance (NHI) system, or at the end of 2010. Cumulative incidences and hazard ratios (HRs) of CRC development were determined.ResultsDuring the first 2 years of follow-up, the subsequent CRC incidence rates in the IBS and comparison cohorts were 37.3 and 5.61 per 10,000 person-years, respectively (adjusted HR, 6.72; 95% CI, 5.70–7.92; p < .0001). Thereafter, the risk did not differ significantly between the 2 cohorts (adjusted HR, 1.08; 95% CI, 0.93–1.26); the participants in the IBS cohort commonly underwent more colonoscopies/sigmoidoscopies than did the non-IBS cohort.ConclusionsIBS was not associated with the long-term development of CRC in Taiwan. The increased risk of CRC in the first 2 years may have occurred because some CRC patients were initially misclassified as IBS patients.