Importance: The frequency and distribution of synucleinopathies and tauopathies manifesting with parkinsonism in the general population are poorly understood, thus affecting health care planning and research.
Objective: To investigate the incidence and distribution of specific types of parkinsonism and related proteinopathies.
Design: We used the medical records-linkage system of the Rochester Epidemiology Project to identify all subjects who received a screening diagnostic code related to parkinsonism in Olmsted County, Minnesota, from January 1, 1991, through December 31, 2005 (15 years). A movement disorders specialist reviewed the complete medical records of each subject who screened positive to determine the type of parkinsonism and the presumed proteinopathy using specified criteria.
Setting: Geographically defined population.
Participants: All residents of Olmsted County who provided authorization to use their data for medical records research (population-based sample).
Main outcome and measures: Incidence of parkinsonism and specific proteinopathies.
Results: Among 542 incident cases of parkinsonism, 409 (75.5%) were classified as proteinopathies. Of the 389 patients with presumed synucleinopathies (71.8%), 264 had Parkinson disease (48.7% of all cases). The incidence rate of synucleinopathies was 21.0 per 100 000 person-years overall and increased steeply with age. The incidence rate of tauopathies was 1.1 overall (20 cases), and the most common tauopathy was progressive supranuclear palsy (16 cases). Thirty-six subjects had drug-induced parkinsonism (6.6%), 11 had vascular parkinsonism (2.0%), 1 had amyotrophic lateral sclerosis in parkinsonism (0.2%), 1 had parkinsonism secondary to surgery (0.2%), and 84 remained unspecified (15.5%). Men had a higher incidence than women for most types of parkinsonism. Findings at brain autopsy confirmed the clinical diagnosis in 53 of 65 patients who underwent autopsy (81.5%).
Conclusions and relevance: The incidence of proteinopathies related to parkinsonism increases steeply with age and is consistently higher in men than women. Clinically diagnosed synucleinopathies are much more common than tauopathies. Findings at autopsy confirm the clinical diagnosis of presumed proteinopathy. Our findings may guide health care planning and prompt new research directions.