Associations between long-term exposure to ambient air pollution and Parkinson's disease prevalence: A...

Epidemiological studies have reported contradictory results regarding the effects of ambient air pollution on Parkinson's disease (PD). This study investigated the associations between long-term exposure to particulate matter <2.5 μm in diameter (PM_2.5) and nitrogen dioxide (NO₂) and PD among participants in the 45 and Up Study, which comprised adults older than 45 years living in New South Wales, Australia.

We conducted a cross-sectional analysis of long-term exposure to PM_2.5 and NO₂ concentrations and prevalence of PD using data from around 240,000 cohort members from the 45 and Up Study, NSW. Annual average concentrations of NO₂ and PM_2.5 were estimated at the participants' residential address using satellite-based land use regression models. Logistic regression was used to quantify the associations between these pollutants and ever physician-diagnosed PD, after adjusting for a range of individual- and area-level covariates.

Among the 236,390 participants with complete data, 1,428 (0.6%) reported physician-diagnosed PD. Annual mean PM_2.5 and NO₂ concentrations for the cohort were 5.8 and 11.9 μg m^-3, respectively, and were positively, but not statistically significantly associated with PD. The odds ratio for a 1 μg m^-3 increase in PM_2.5 was 1.01 (95% confidence interval (CI): 0.98-1.04). The adjusted odds ratio for a 5 μg m^-3 increase in NO₂ was 1.03 (95% CI: 0.98-1.08). In subgroup analyses, larger associations for NO₂ were observed among past smokers (OR 1.11 (95% CI: 1.02-1.20) per 5 μg m^-3 increase).

Overall, we found limited evidence of associations between long-term exposure to NO₂ or PM_2.5 and PD. The associations observed among past smokers require further corroboration.