Several studies with animal research associate air pollution in Alzheimer's disease (AD) neuropathology, but the actual impact of air pollution on the risk of AD is unknown. Here, this study investigates the association between long-term exposure to ozone (O3) and particulate matter (PM) with an aerodynamic diameter equal to or less than 2.5 μm (PM2.5), and newly diagnosed AD in Taiwan. We conducted a cohort study of 95,690 individuals' age ≥ 65 during 2001-2010. We obtained PM10 and O3 data from Taiwan Environmental Protection Agency during 2000-2010. Since PM2.5 data is only accessible entirely after 2006, we used the mean ratio between PM2.5 and PM10 during 2006-2010 (0.57) to estimate the PM2.5 concentrations from 2000 to 2005. A Cox proportional hazards model was used to evaluate the associations between O3 and PM2.5 at baseline and changes of O3 and PM2.5 during the follow-up period and AD. The adjusted HR for AD was weakly associated with a raised concentration in O3 at baseline per increase of 9.63 ppb (adjusted HR 1.06, 95% confidence interval (CI) 1.00-1.12). Further, we estimated a 211% risk of increase of AD per increase of 10.91 ppb in O3 over the follow-up period (95% CI 2.92-3.33). We found a 138% risk of increase of AD per increase of 4.34 μg/m3 in PM2.5 over the follow-up period (95% CI 2.21-2.56). These findings suggest long-term exposure to O3 and PM2.5 above the current US EPA standards are associated with increased the risk of AD.
Keywords: Air pollution; Alzheimer's disease; neurodevelopment; ozone; particulate matter.