OBJECTIVES:

To determine whether irritable bowel syndrome (IBS) is associated with an increased risk for the subsequent colorectal cancer (CRC).

METHODS:

We 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.

RESULTS:

During the first 2years of follow-up, the subsequent CRC incidence rates in the IBS and comparison cohorts were 37.3 and 5.61 per 10,000person-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.

CONCLUSIONS:

IBS was not associated with the long-term development of CRC in Taiwan. The increased risk of CRC in the first 2years may have occurred because some CRC patients were initially misclassified as IBS patients.