Association between exposure to PM2.5 components and disease aggravation in Parkinson’s disease: an analysis in New York State

Abstract

BACKGROUND AND AIM: Studies suggests that long-term fine particle matter (PM2.5) exposure may contribute to aggravation of Parkinson’s disease (PD), but overall results have been inconsistent. Among other factors, the differences may arise from variations in PM2.5 composition. In a previous study in New York State, we found a nonlinear PM2.5–PD association. To further characterize this association, here we evaluated long-term exposure to specific PM2.5 components in the same cohort. METHODS: We used data from the New York Department of Health Statewide Planning and Research Cooperative System (2000–2014) to construct annual county counts of first hospitalizations with a PD diagnosis. We used well-validated prediction models at 1km2 resolution to calculate county-level population-weighted annual concentrations of six PM2.5 components: black carbon, organic matter, nitrate, sulfate, sea salt, and soil. Exposure was assigned based on county of residence. We used mixed quasi-Poisson models with county-specific random intercepts to estimate rate ratios (RRs) and 95% confidence intervals (CI) for a 1-year exposure to each PM2.5 component. We allowed for nonlinear exposure–outcome relationships using penalized splines and accounted for potential geospatial and temporal confounders. RESULTS:We estimated a linear positive association between organic matter and disease aggravation in PD (RR=1.06, 95%CI: 1.04, 1.09 per one standard deviation (SD) increase) and a positive linear association with nitrate (RR=1.06, 95%CI: 1.03, 1.10 per one SD increase). We found no association with sulfate, sea salt, or soil exposure. CONCLUSIONS:Our results support that particle composition of PM2.5 may influence its adverse effects on PD. Specifically, we identified organic matter and nitrate as potentially important components in the PD–PM2.5 association. KEYWORDS: Air pollution, particle composition, Parkinson's disease, long-term exposures, disease aggravation