Ambient Air Pollution Exposures and Risk of Parkinson Disease.
BACKGROUND
Few epidemiologic studies have evaluated the effects of air pollution on the risk of Parkinson disease (PD).


OBJECTIVE
We investigated the associations of long-term residential concentrations of ambient particulate matter (PM) < 10 μm in diameter (PM10) and < 2.5 μm in diameter (PM2.5) and nitrogen dioxide (NO2) in relation to PD risk.


METHODS
Our nested case-control analysis included 1,556 self-reported physician-diagnosed PD cases identified between 1995 and 2006 and 3,313 controls frequency-matched on age, sex, and race. We geocoded home addresses reported in 1995-1996 and estimated the average ambient concentrations of PM10, PM2.5, and NO2 using a national fine-scale geostatistical model incorporating roadway information and other geographic covariates. Air pollutant exposures were analyzed as both quintiles and continuous variables, adjusting for matching variables and potential confounders.


RESULTS
We observed no statistically significant overall association between PM or NO2 exposures and PD risk. However, in preplanned subgroup analyses, a higher risk of PD was associated with higher exposure to PM10 (ORQ5 vs. Q1 = 1.65; 95% CI: 1.11, 2.45; p-trend = 0.02) among women, and with higher exposure to PM2.5 (ORQ5 vs. Q1 = 1.29; 95% CI: 0.94, 1.76; p-trend = 0.04) among never smokers. In post hoc analyses among female never smokers, both PM2.5 (ORQ5 vs. Q1 = 1.79; 95% CI: 1.01, 3.17; p-trend = 0.05) and PM10 (ORQ5 vs. Q1 = 2.34; 95% CI: 1.29, 4.26; p-trend = 0.01) showed positive associations with PD risk. Analyses based on continuous exposure variables generally showed similar but nonsignificant associations.


CONCLUSIONS
Overall, we found limited evidence for an association between exposures to ambient PM10, PM2.5, or NO2 and PD risk. The suggestive evidence that exposures to PM2.5 and PM10 may increase PD risk among female never smokers warrants further investigation. Citation: Liu R, Young MT, Chen JC, Kaufman JD, Chen H. 2016. Ambient air pollution exposures and risk of Parkinson disease. Environ Health Perspect 124:1759-1765; http://dx.doi.org/10.1289/EHP135.
Epidemiology Branch, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina, USA.
Rui
R
Liu
Michael T
MT
Young
Jiu-Chiuan
JC
Chen
Joel D
JD
Kaufman
Honglei
H
Chen
D000368:Aged; D016022:Case-Control Studies; D015331:Cohort Studies; D004784:Environmental Monitoring; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009585:Nitrogen Dioxide / Q000032:analysis / Q000633:toxicity; D010300:Parkinson Disease / Q000453:epidemiology*; D010316:Particle Size; D052638:Particulate Matter / Q000032:analysis* / Q000633:toxicity; D018570:Risk Assessment
D052638:Particulate Matter; D009585:Nitrogen Dioxide