Prevalence of tremor and Parkinson's disease.

To determine the prevalence of essential tremor (ET) and Parkinson's disease (PD) in a retirement community, all residents of Carefree, Arizona, aged over 65 years were contacted. All participants completed validated questionnaires for PD and ET, and were examined using the Unified Parkinson's Disease Rating Scale. Of 356 individuals evaluated, 155 (43.5%) had tremor; 73 (20.5%) had ET; 26 (7.3%) had PD; and 56 (15.7%) had postural tremor (PT). Thus, a large percentage of individuals were found to have tremor, in the plurality of whom it could be classified as ET. The number of individuals with Parkinson's disease exceeded our expectations.