Natural History of Parkinson's Disease in the Province of Segovia: Disability in a 20 Years Longitudinal Study.

BACKGROUND: Parkinson's disease mainly affects the elderly population causing a progressive functional disability with motor, psychic, and cognitive deterioration. OBJECTIVE: This study was carried out to evaluate disability caused by Parkinson's disease by analyzing the median time to reach Hoehn and Yahr stage III and to investigate predictor variables based on a 20-year longitudinal follow-up study. METHODS: We examined 273 patients with Parkinson's disease recruited between 1978 and 1998. We performed a survival analysis using the Kaplan-Meier method to determine the time to disability and we used a Cox regression model to adjust prognosis factors. RESULTS: The median time to reach Hoehn and Yahr stage III was 7.73 years (95% CI: 5.95-8.05). Independent predictors of disability were: age at onset, the hazard ratio (HR) = 1.10, 95% CI: 1.08-1.12; UPDRS II (activities of daily living) HR = 1.08, 95% CI: 1.03-1.14; and akinesia and rigidity at onset HR = 1.55, 95% CI: 1.07-2.24. CONCLUSIONS: Patients with Parkinson's disease evolve gradually toward disability, and prognostic factors of this evolution were identified.