Levodopa-dyskinesia incidence by age of Parkinson's disease onset.

We assessed the 5-year risk of levodopa-induced dyskinesias by age of Parkinson's disease (PD) onset in a population-based cohort. The medical records linkage system of the Rochester Epidemiology project was used to identify residents of Olmsted County, Minnesota, with incident PD for the period 1976 through 1990. In this population-based study, the 5-year dyskinesia incidence declined with age. With PD onset after 70 years of age, the incidence was 16%. With onset from 40 to 59 years of age, the incidence was higher at 50%. These incidence data may overestimate the functional importance, because patients with minimal or reversible dyskinesias were counted.