Traffic-Related Air Pollution and Parkinson's Disease in Denmark: A Case-Control Study

Environ Health Perspect. 2015 Jul 7. [Epub ahead of print]

Ritz B, Lee PC, Hansen J, Funch Lassen C, Ketzel M, Sørensen M, Raaschou-Nielsen O.

OBJECTIVE:

Very little is currently known about air pollutants' adverse effects on neurodegenerative diseases even though recent studies have linked particulate exposures to brain pathologies associated with Parkinson's and Alzheimer's disease. Here we investigate long-term exposure to traffic-related air pollution and Parkinson's disease.

METHODS:

In a case-control study of 1,696 Parkinson's disease (PD) patients identified from Danish hospital registries and diagnosed 1996-2009 and 1,800 population controls matched by gender and year of birth we assessed long-term traffic-related air pollutant exposures (NO2) from a dispersion model, using residential addresses from 1971 to the date of diagnosis or first cardinal symptom for cases and the corresponding index date for their matched controls. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated with logistic regression adjusting for matching factors and potential confounders.

RESULTS:

We found ambient air pollution from traffic sources to be associated with risk of PD, with a 9% higher risk (95% CI: 3, 16.0%) per interquartile range increase (2.97 μg/m3) in modeled NO2. For participants living for 20 years or more in the capital city odds ratios were larger (OR= 1.21; 95% CI: 1.11, 1.31) than in provincial towns (OR=1.10; 95% CI: 0.97, 1.26), while there was no association among rural residents.

CONCLUSIONS:

Our findings raise concerns about potential effects of air pollution from traffic and other sources on the risk of PD, particularly in populations with high or increasing exposures.