Trends in Irritable Bowel Syndrome Incidence among Taiwanese Adults during 2003-2013: A Population-Based Study of Sex and Age Differences.

Background: No population-based irritable bowel syndrome (IBS) incidence data among Taiwanese adults are available. Whether IBS is associated with risk of organic colonic diseases remains unanswered. We investigated 1) the sex- and age-stratified trends in the annual incidence of IBS, and 2) the risk of selected organic diseases in patients with IBS compared with those without IBS among Taiwanese adults during 2003-2013.

Methods: Medical claims data for 1 million randomly selected beneficiaries were obtained and analyzed. Patients with IBS were considered eligible for enrollment if they aged between 20 and 100 and had at least two medical encounters with IBS codes within 1 year. To test whether there was a linear secular trend in IBS incidence over time, multivariate Poisson regression with generalized estimating equation model was conducted. The risk of selected organic diseases associated with IBS was examined using multivariate Cox proportional hazard regression.

Results: From 2003 to 2013, the incidence of IBS significantly decreased over time [adjusted incidence rate ratio (IRR) = 0.97, p< 0.001]; the incidence of IBS significantly increased with age (adjusted IRR = 1.03, p < 0.001) and was significantly higher in women than in men (adjusted IRR = 1.14, p< 0.001). IBS significantly associated with increased risk of microscopic colitis, inflammatory bowel disease, and colorectal cancer during a 10-year follow-up period.

Conclusions: The incidence of IBS increased with age and was slightly higher in women than in men among Taiwanese adults. During 2003-2013, IBS incidence gradually decreased over time. IBS may increase risk of several colonic organic diseases.