Incident parkinsonism in older adults without Parkinson disease.

OBJECTIVE: To determine the incidence of parkinsonism in community-dwelling older adults without Parkinson disease.

METHODS: Four parkinsonian signs were assessed with a modified motor portion of the Unified Parkinson's Disease Rating Scale in 2,001 older adults without parkinsonism. We used Cox proportional hazards models to determine the associations of age and sex with incident parkinsonism (2 or more signs). We calculated the number of events per 1,000 person-years of observation in 3 age strata. Next, we investigated several potential risk factors for incident parkinsonism. Then, we examined longitudinal progression of parkinsonism using discrete-time multistate Markov models.

RESULTS: Average age at baseline was 76.8 years (SD 7.62 years). During an average of 5 years of follow-up, 964/2,001 (48.2%) developed parkinsonism. Age (hazard ratio [HR] 1.09, 95% confidence interval [CI] 1.08-1.10) but not male sex (HR 1.06, 95% CI 0.91-1.23) was associated with incident parkinsonism. The incidence of parkinsonism per 1,000 person-years of follow-up was 36.0 for adults <75 years of age, 94.8 for those 75-84, and 160.5 for those 85 years or older. Depressive symptoms, neuroticism, urinary incontinence, sleep complaints, and chronic health conditions were associated with incident parkinsonism. Secondary analyses suggest that risk factors are linked with incident parkinsonism via early motor signs of parkinsonism and cognitive function. Transition modeling suggests that while parkinsonism may fluctuate, it is progressive in most older adults and its risk factors increase the odds of its progression.

CONCLUSIONS: Parkinsonism is common in older adults and increases with age. Identifying modifiable risk factors may decrease the magnitude of this growing public health problem.