Fine Particle Exposure and Clinical Aggravation in Neurodegenerative Diseases in New York State

BACKGROUND: Adult-onset neurodegenerative diseases affect millions and negatively impact health care systems worldwide. Evidence suggests that air pollution may contribute to aggravation of neurodegeneration, but studies have been limited. OBJECTIVE: We examined the potential association between long-term exposure to particulate matter [Formula: see text] in aerodynamic diameter [fine particulate matter ([Formula: see text])] and disease aggravation in Alzheimer’s (AD) and Parkinson’s (PD) diseases and amyotrophic lateral sclerosis (ALS), using first hospitalization as a surrogate of clinical aggravation. METHODS: We used data from the New York Department of Health Statewide Planning and Research Cooperative System (SPARCS 2000–2014) to construct annual county counts of first hospitalizations with a diagnosis of AD, PD, or ALS (total, urbanicity-, sex-, and age-stratified). We used annual [Formula: see text] concentrations estimated by a prediction model at a [Formula: see text] resolution, which we aggregated to population-weighted county averages to assign exposure to cases based on county of residence. We used outcome-specific mixed quasi-Poisson models with county-specific random intercepts to estimate rate ratios (RRs) for a 1-y [Formula: see text] exposure. We allowed for nonlinear exposure–outcome relationships using penalized splines and accounted for potential confounders. RESULTS: We found a positive nonlinear [Formula: see text] association that plateaued above [Formula: see text] ([Formula: see text] , 95% CI: 1.04, 1.14 for a [Formula: see text] increase from 8.1 to [Formula: see text]). We also found a linear [Formula: see text] positive association ([Formula: see text] , 95% CI: 1.01, 1.09 per [Formula: see text] [Formula: see text] increase), and suggestive evidence of an association with AD. We found effect modification by age for PD and ALS with a stronger positive association in patients [Formula: see text] of age but found insufficient evidence of effect modification by sex or urbanization level for any of the outcomes. CONCLUSION: Our findings suggest that annual increase in county-level [Formula: see text] concentrations may contribute to clinical aggravation of PD and ALS. Importantly, the average annual [Formula: see text] concentration in our study was [Formula: see text] , below the current American national standards, suggesting the standards may not adequately protect the aging population. https://doi.org/10.1289/EHP7425