Factor structure of parkinsonian signs in the community-dwelling elderly

Parkinsonian signs are present in 40% of older people. Factor analysis of the motor section of the Unified Parkinson's Disease Rating Scale (UPDRS) in patients with Parkinson's disease (PD) has identified several principal domains, including rigidity, axial function, and rest tremor. We hypothesized that if Parkinsonian signs in the elderly were due to basal ganglia dysfunction that this same constellation of factors (rigidity, axial function, rest tremor) would emerge in a factor analysis. We carried out factor analysis, using the principal component method with orthogonal (varimax) rotation, on motor UPDRS scores in community-dwelling elderly without PD. A modified (10-item) version of the motor portion of the UPDRS was administered to 1,339 older adults living in the Washington Heights-Inwood community and it was found that Parkinsonian signs were present in 537 (40.1%). Three factors (rigidity, axial function. and rest tremor) were obtained from the factor analysis and, together, explained 67.4% of the variance. A second factor analysis was carried out excluding the 26 participants with rest tremor, and two factors (rigidity, axial function) emerged. These data support the view that Parkinsonian signs in older adults might be due to basal ganglia dysfunction, a possibility that requires further exploration.