Time trends in the prevalence and incidence of Parkinson's disease in Taiwan: A nationwide, population-based study.

BACKGROUND/PURPOSE Identifying trends in the prevalence and incidence of Parkinson's disease (PD) may yield information that supports public health goals. Our aim was to evaluate time-trend changes in the prevalence and incidence of PD in Taiwan between 2004 and 2011. METHODS This retrospective, nationwide, longitudinal study used the Taiwan National Health Insurance Research Database to identify patients with PD from 2004 to 2011 based on having ICD-9-CM diagnostic codes, which were assigned by neurologists, and being prescribed PD medication. Annual incidence and prevalence were calculated, and time-trend analyses were estimated assuming a Poisson distribution. RESULTS Over the study period, 19,302 patients in 2004 and 41,606 patients in 2011 fulfilling the study criteria for PD were included in the analysis. The average age-standardized prevalence of PD per 100,000 of population was 84.8 in 2004 and 147.7 in 2011, with a 7.9% yearly increase. Increasing prevalence trends of PD were statistically significant (p < 0.001) in all age groups, with the steepest rate among those aged ≥ 80 years. In contrast, the average age-standardized incidence of PD decreased steadily from 35.3 per 100,000 in 2005 to 28.8 per 100,000 in 2011. The incidence rate was higher in men than in women, and increased with age. CONCLUSION We identified an increasing trend in the annual prevalence rates of PD from 2004 to 2011; however, the substantial decline in the incidence of PD suggests that some major environmental risk factors for PD were removed from this population during this time period.