The etiology of Parkinson’s disease (PD) is multifactorial and involves both genetic and nongenetic factors. Several studies have linked air pollution, in the form of particulate matter with a diameter <2.5 μm (PM2.5), to various disorders including cardiovascular disease, dementia and stroke. The ultrafine particles (≤0.1 μm) in PM2.5 cross the blood-brain barrier. Some subcomponents can contain metals, including arsenic and manganese, that have been implicated with the neuropathogenesis of basal ganglia degeneration.
Results
In a large study comprising 21.6 million Medicare beneficiaries across the United States, the association between ambient PM2.5 levels and incident PD was assessed. Exposure to PM2.5 was estimated based on modeled PM2.5 levels at the geographic residence code from 1998 to 2000. Cases with incident PD were identified based on the presence of a first diagnostic code of PD in 2009, which occurred in 89,390 individuals. Analyses were adjusted for age, sex, race, estimated smoking and health care utilization. The main finding was that higher annual PM2.5 levels were associated with an increased risk of PD. The relative risk of PD was 56% greater for those exposed to the median level of PM2.5 compared to the lowest.
Conclusion
This is the largest study on this topic so far. The study included a comprehensive population-based capture of beneficiaries instead of recruitment through hospitals. A strength of this analysis is the inclusion of a 10-year lag between the assessment of PM2.5 exposure and the incidence of PD, because the relevant period of exposure precedes the clinical manifestation of PD by many years. Despite limitations, such as confounding factors by other air pollutants implicated as possible risk factors for PD, this study advances current knowledge of the relationship between air pollution and PD risk.
Krzyzanowski B, Searles Nielsen S, Turner JR, Racette BA. Fine Particulate Matter and Parkinson Disease Risk Among Medicare Beneficiaries. Neurology. 2023 Nov;101(21):e2058-67. Epub 2023 Oct 30.
