Increased risk of overactive bladder in patients with idiopathic Parkinson’s disease: Insight from a nationwide population-based cohort study

Background: Idiopathic Parkinson’s disease (IPD) is a progressive neurodegenerative disorder characterized by typical motor impairment. However, lower urinary tract symptoms, including urinary urgency or frequency, which are non-motor phenomena, occur frequently among patients with IPD. In this study, we assess the risk of overactive bladder (OAB) in patients with IPD. Methods: The National Health Insurance Research Database of Taiwan was used to identify patients with IPD (IPD cohort) and four-fold controls (non-IPD cohort) from 2000 to 2010. The non-IPD cohort was matched according to age, sex, and baseline comorbidities, including benign prostate hyperplasia, stress incontinence, diabetes, and cerebrovascular diseases. The occurrence of OAB was monitored until the end of 2011. Hazard ratios of OAB were estimated using Cox proportional hazards regression models. Results: In total, 4,571 and 18,255 patients were included in IPD and non-IPD cohorts, respectively. Results showed a significantly higher overall incidence rate of OAB in the IPD cohort compared with the non-IPD cohort (14.5 vs. 6.37 per 10,000 person-years), with a 2.3-fold increased risk of OAB (95% confidence interval [CI] = 1.51–3.51) after controlling for benign prostate hyperplasia and stress incontinence. The mean follow-up period for the IPD cohort was 5.0 years. This cohort study showed that the cumulative incidence of OAB was 0.65% at the fifth year and 1.54% at the tenth year after IPD diagnosis; this risk was highest in the age group 65–74 years. Conclusion: This study reveals that IPD is independently associated with an increased risk of OAB in patients with IPD. The probability of OAB was 1.54% over a 10-year period after IPD diagnosis; the risk of OAB is considered to be age-dependent and most substantial in patients aged 65–74 years.