Objective: Limited information is available on the frequency and distribution of parkinsonism as a syndrome. We studied the incidence of parkinsonism and its specific types among residents of Olmsted County, MN, for the period from 1976 through 1990.

Methods: We used the medical records linkage-system of the Rochester Epidemiology Project to identify all individuals whose records contained documentation of any form of parkinsonism, related neurodegenerative diseases, or tremor of any type. A nurse abstractor screened the records, and, when applicable, a neurologist reviewed them to determine the presence of parkinsonism using specified diagnostic criteria and to define the year of onset.

Results: We found 364 incident cases of parkinsonism: 154 with PD (42%), 72 with drug-induced parkinsonism (20%), 61 unspecified (17%), 51 with parkinsonism in dementia (14%), and 26 with other causes (7%). The average annual incidence rate of parkinsonism (per 100,000 person-years) in the age group 50 to 99 years was 114.7; incidence increased steeply with age from 0.8 in the age group 0 to 29 years to 304.8 in the age group 80 to 99 years. The cumulative incidence of parkinsonism assuming no competing causes of death was 7.5% to age 90 years. PD was the most common type of parkinsonism, followed by parkinsonism in dementia in men and drug-induced parkinsonism in women. Men had higher incidence than women at all ages for all types of parkinsonism except drug-induced.

Conclusions: Parkinsonism is a common disease among the elderly; its incidence increases steeply with advancing age and is consistently higher in men. The distribution by type changes with age and gender.