Dimensionality of parkinsonian signs in aging and Alzheimer's disease

Background. Parkinsonian signs are commonly found on the neurologic examina tion of older persons and are associated with morbidity and mortality. The extent to which parkinsonian signs in aging and Alzheimer's disease cluster in groups typical of Parkinson's disease has not been investigated previou sly. Methods. The motor portion of the Unified Parkinson's Disease Rating Scale (UPDRS), or a version with minor modifications, was administered to more th an 2,800 persons in three cohorts: (a) 637 older persons with a wide range of neurologic conditions participating in the Chicago Health and Aging Proj ect, a study of common health problems of a random sample of older persons from a geographically defined biracial community population; (b) 638 relati vely healthy and highly educated older persons from 25 Catholic religious c ommunities participating in the Religious Orders Study, a longitudinal clin ical-pathologic study of aging; and (c) 1,546 older persons undergoing eval uation for possible dementia at the Push Alzheimer's Disease Center, an urb an, tertiary care center that evaluates persons for possible dementia. Sepa rate factor analyses were performed on each data set. Additional analyses e xamined the factor structure in subsets by gender and race, Results. A similar grouping of items emerged in each cohort and did not dif fer substantially by gender or race. The factors corresponded closely with the traditional grouping of parkinsonian signs into bradykinesia, gait dist urbance, rigidity, and tremor. Conclusions. The grouping of parkinsonian si,ans is consistent in diverse s amples of older persons and does not vary substantially across gender or ra ce. The results provide an empirical basis for summarizing the principal mo toric manifestations of parkinsonism.