A longitudinal study of parkinsonism and disability in a community population of older people

Background. Parkinsonian signs in patients without Parkinson's disease are often undetected but occur frequently in older people, and are often considered benign. We measured the association between parkinsonism and subsequent disability. Methods. We conducted a prospective, longitudinal, community-based population study in East Boston, Massachusetts, using a stratified random sample of 455 community residents, aged 65 years and older. Four categories of parkinsonian signs were measured at baseline: bradykinesia, gait disturbance, rigidity, and tremor. Parkinsonism was defined as the presence of two or more categories of parkinsonian signs, and cases of Parkinson's disease were excluded from analyses. Disability was assessed annually over a mean of 4.7 years using the Katz, Rosow-Breslau, and Nagi disability measures. Results. Parkinsonism at baseline strongly predicted subsequent disability as assessed with the three disability measures (on the Katz measure, β = -1.30, p < .001). On average, a person with parkinsonism had a disability level at follow-up equal to that of a comparable person approximately 16.7 years for men and 8 years for women. The rate of developing disability for persons with parkinsonism increased each year; on the Katz measure, participants with parkinsonism declined on average 16.4% faster than those without. Gait impairment and bradykinesia strongly predicted subsequent disability; tremor and rigidity did not. The effect of parkinsonism was attenuated but still persistent in persons with coexistent moderate-to-severe cognitive impairment or stroke. Conclusions. Parkinsonism strongly predicts progressive disability in the older community population and has a marked aging effect on disability level.