The risk of irritable bowel syndrome in patients with endometriosis during a 5-year follow-up: a nationwide population-based cohort study.

PURPOSE: Studies have suggested that endometriosis may coexist with irritable bowel syndrome (IBS). Using a population-based cohort study, we followed subjects for a 5-year period to identify the risk of IBS after a diagnosis of endometriosis. METHODS: This cohort study used the Taiwan National Health Insurance Database as a source of subjects. A total of 6076 patients with endometriosis from 2000 to 2005 were identified. Their data were compared with those of 30,380 age-matched controls without endometriosis who were randomly selected from the same database. All subjects were tracked for 5 years from the date of cohort entry to identify the risk of IBS. The Cox model was used to evaluate the 5-year event occurrence of IBS. RESULTS: Nine hundred twenty-six patients were diagnosed with IBS, including 256 in the case cohort (4.2%) and 670 in the control cohort (2.2%). The Kaplan-Meier survival curves demonstrated significantly lower event-free rates in the case cohort than in the control cohort (P = 0.001). After adjusting for urbanization level, monthly income, residential region and comorbidities, the hazard ratio (HR) within 5 years revealed a 1.79-fold (95% confidence interval [CI] 1.55-2.07) greater risk among the cases than the controls. The HR was higher within the first year of follow-up (HR 1.90, 95% CI 1.42-2.55) and in those women aged 25-34 years (HR 2.17, 95% CI 1.61-2.92). CONCLUSIONS: The risk of IBS among endometriosis patients persisted over 5 years of follow-up. The association detected in this study might have proceeded through shared risk and pathogenic factors.