Dementia-Free Survival and Risk Factors for Dementia in a Hospital-Based Korean Parkinson's Disease Cohort

BACKGROUND AND PURPOSE Few studies of dementia in Parkinson's disease (PD) have had long-term follow-ups. Moreover, information on the duration from the onset to the development of dementia in patients with PD is lacking. The aim of this study was to determine the median dementia-free survival time from the onset of PD to the development of dementia. METHODS In total, 1,193 Korean patients with PD were recruited and assessed at regular intervals of 3-6 months. We interviewed the patients and other informants to identify impairments in the activities of daily living. The Hoehn and Yahr stage and scores on the Unified Parkinson's Disease Rating Scale and Mini Mental State Examination were evaluated annually. We used Kaplan-Meier survival analysis to estimate the cumulative proportion of dementia-free patients over time. Risk factors predicting dementia were also evaluated using Cox proportional-hazards regression models. RESULTS The median dementia-free survival time in the Korean PD population was 19.9 years. Among the 119 patients who subsequently developed dementia, the mean duration from the onset of PD to the development of dementia was 10.6 years. A multivariate analysis identified age at onset and education period as the significant predictors of dementia. CONCLUSIONS This is the first report on dementia-free survival in patients with PD based on longitudinal data analysis from the disease onset. The median dementia-free survival time in Korean PD patients was found to be longer than expected.