Irritable bowel syndrome and subsequent risk of Parkinson's disease: a nationwide population-based matched-cohort study

Background: Gastrointestinal dysfunction (GI) is the most prevalent non-motor symptom of Parkinson's disease (PD), and its role in the risk of PD has been studied. In this study, we tried to evaluate whether irritable bowel syndrome (IBS) increased the risk of PD development stratified by sex, age, and IBS duration using a large nationwide cohort in Korea. Methods: Patients aged ≥ 20 years with a primary diagnosis of IBS (ICD-10 codes: G56) more than three times were selected. A randomly matched cohort without IBS was enrolled by exact matching patients for sex, age, socioeconomic status, comorbidities, and year of enrollment to the IBS group with a ratio of 1:3. Cause-specific Cox regression models were used to identify hazards associated with PD development depending on the presence of IBS during the 11-year follow-up period. Results: In total, 285,064 patients were enrolled in the study: 71,806 in the IBS cohort and 213,258 in the comparison cohort. Cause-specific Cox regression model showed a hazard ratio of 1.436 (95% CI, 1.226-1.682) for PD development in the IBS cohort, which is consistent in both male and female sexes. Subgroup analyses according to age groups showed that IBS increased PD risk only in individuals ≥ 65 years (HR = 1.449, 95% CI, 1.207-1.741). Conclusions: We found temporal relationship between IBS and PD at aged ≥ 65 years. There might be a possibility that IBS was an early manifestation of PD, and future studies for causal link between the two diseases to elucidate biomechanism are warranted.restrictio