Parkinson's disease and long-term exposure to outdoor air pollution: A matched case-control study in the Netherlands

Background: There is some evidence to suggest an association between ambient air pollution and development of Parkinson's disease (PD). However, the small number of studies published to date has reported inconsistent findings.

Objectives: To assess the association between long-term exposure to ambient air pollution constituents and the development of PD.

Methods: Air pollution exposures (particulate matter with aerodynamic diameter <10 μm [PM₁₀], <2.5 μm [PM_2.5], between 2.5 μm and 10 μm [PM_coarse], black carbon, and nitrogen oxides [NO₂ and NO_x]) were predicted based on land-use regression models developed within the "European Study for Air Pollution Effects" (ESCAPE) study, for a Dutch PD case-control study. A total of 1290 subjects (436 cases and 854 controls). were included and 16 years of exposure were estimated (average participant starting age: 53). Exposures were categorized and conditional logistic regression models were applied to evaluate the association between ambient air pollution and PD.

Results: Overall, no significant, positive relationship between ambient air pollutants and PD was observed. The odds ratio (OR) for PD associated with an increase from the first quartile of NO₂ (<22.8 μg/m³) and the fourth (>30.4 μg/m³) was 0.87 (95% CI: 0.54, 1.41). For PM_2.5 where the contrast in exposure was more limited, the OR associated with an increase from the first quartile PM_2.5 (<21.2 μg/m3) to the fourth (>22.3 μg/m3) was 0.50 (95% CI: 0.24, 1.01). In a subset of the population with long-term residential stability (n = 632), an increased risk of PD was observed (e.g. OR for Q4 vs Q1 NO₂:1.37, 95% CI: 0.71, 2.67).

Conclusions: We found no clear association between 16 years of residential exposure to ambient air pollution and the development of PD in The Netherlands.