Mild parkinsonian signs and plasma homocysteine concentration in community-dwelling elderly individuals

Objective: To determine whether plasma homocysteine (Hcy) concentration is associated with mild parkinsonian signs (MPS) in community-dwelling elderly individuals. Design: Cross-sectional analyses of a population-based cohort study. Setting: Washington Heights-Inwood, New York. Patients: Persons without dementia 65 years and older. Main Outcome Measure: Participants underwent an abbreviated motor portion of the Unified Parkinson's Disease Rating Scale. Each participant was assigned an MPS score (range, 0-40). The Hcy concentration was measured from plasma. All analyses were cross-sectional. Results: There were 369 participants (mean ± SD age, 77.8 ± 6.0 years; mean ± SD MPS score, 1.51 ± 2.55; mean ± SD plasma Hcy concentration, 17.3 ± 6.5 μmol/L). Mean ± SD MPS scores in plasma Hcy concentration quintiles were as follows: lowest quintile, 1.15 ± 1.77; second quintile, 1.18 ± 1.88; third quintile, 1.64 ± 2.93; fourth quintile, 1.45 ± 2.17; and highest quintile, 2.12 ± 3.49 (84.3% higher than 1.15) (P=.02). In an unadjusted linear regression model, plasma Hcy concentration was associated with log MPS score (dependent variable) (P=.008). In a linear regression model that adjusted for confounding variables, plasma Hcy concentration was associated with log MPS score (P=.04). Conclusions: These data indicate that MPS are associated with higher plasma Hcy concentrations. Prospective neuroimaging as well as clinical-pathological studies would further our understanding of several mechanisms that could underlie the observed association.