Long-term effect of fine particulate matter on hospitalization with dementia

Background: New evidence suggests that particulate matter less than 2.5 mu m in diameter (PM2.5) is associated with late-onset dementia (LOD). However, epidemiological studies for the entire population are lacking. Methods: We analyzed approximately 94 million follow-up records from fee-for-service Medicare records for 13 million Medicare beneficiaries residing in the southeastern United States (U.S.) from 2000 to 2013. We used spatially and temporally continuous PM2.5 exposure data. To account for time-varying PM2.5 levels, we applied an Andersen-Gill counting process proportional hazard model; we stratified our analyses by subtype of dementia and level of urbanization of residence. Results: During a median follow-up of 6 years, 1,409,599 hospitalizations with dementia occurred. The adjusted hazard ratio (FIR) of hospitalization with dementia was 1.049 (95% confidence interval [CI], 1.048 to 1.051) per 1 mu g/m(3) increase in annual PM2.5. The hazard ratio for vascular dementia was higher (FIR, 1.086; 95% CI, 1.082 to 1.090). In large, the magnitude of the effect grew as the level of urbanization increased (HR, 1.036; 95% CI, 1.031 to 1.041 in rural areas versus HR. 1.052; 95% CI, 1.050 to 1.054 in metropolitan areas). Conclusions: Long-term exposure to higher PM2.5 was associated with increased hospitalizations with dementia. (C) 2019 Elsevier Ltd. All rights reserved.