Abstract
The authors tested the hypothesis that difficulty in identifying odors, a common finding in Parkinson's disease, is associated with more rapid progression of parkinsonian signs in 743 community-dwelling older people without dementia or Parkinson's disease at study onset. Odor identification ability was assessed at baseline with the 12-item Brief Smell Identification Test (mean = 9.0 correct, SD = 2.1), and parkinsonism was assessed annually for up to 5 years with a modified version of the Unified Parkinson's Disease Rating Scale. In an analysis adjusted for age, sex, and education, lower odor identification score was related to higher level of global parkinsonism at baseline (p < .001) and more rapid progression of global parkinsonism on follow-up (p = .002). This result mainly reflected an association of odor identification with worsening parkinsonian gait. The results suggest that impaired odor identification is associated with more rapid progression of parkinsonism in old age, particularly parkinsonian gait disturbance.
This research was supported by National Institute on Aging grants R01 AG17917, R01 AG022018, and R01 AG024480, and the Illinois Department of Public Health. We thank the many Illinois residents for participating in the Rush Memory and Aging Project; Traci Colvin, MPH, and Tracy Hagman for coordinating the study; Zhaotai Cui, MS, for statistical programming; George Dombrowski, MS, and Greg Klein for data management; and Valerie J. Young for preparing the manuscript.
Notes
∗Values are mean and standard deviation unless otherwise indicated. MMSE is for Mini-Mental State Examination.
∗Based on square root transformation of raw scores or the presence of a nonzero score.
∗From a generalized estimating equation model adjusted for age, sex, and education.