Association of tailpipe-related and nontailpipe-related air pollution exposure with neuroimaging outcomes

Long-term exposure to air pollution may be related to neural atrophy or cerebrovascular pathology. A major source of air pollution is vehicle traffic, which is modifiable. In this study, we estimated associations between four traffic-related air pollutants and five neuroimaging biomarkers.

We analyzed data from a subset (N = 817) of participants in the Chicago Health and Aging Project (1993-2012) who underwent a structural magnetic resonance imaging (MRI) scan between 2002 and 2012. Using previously developed air pollution models, we predicted participant-level exposure to the tailpipe pollutants oxides of nitrogen (NO_X) and nitrogen dioxide (NO₂), plus the nontailpipe pollutants copper and zinc found in coarse particulate matter (PM_10-2.5,Cu and PM_10-2.5,Zn, respectively) over the 3 years before each participants' first MRI scan date. Using linear regression, we estimated cross-sectional, covariate-adjusted associations between each pollutant with total cerebral volume, total hippocampal volume, total lateral ventricle volume, total white matter hyperintensity volume, and cortical thickness. These models incorporated inverse probability weights to account for potential selection biases driven by differences between participants who did and did not undergo an MRI scan after being offered one.

Exposure to NO_X and NO₂ was associated with less cortical thickness on average (-0.06 mm, 95% confidence interval [CI] = -0.09, -0.02 per 7.8 ppb NO_X; -0.04 mm, 95% CI = -0.07, -0.01 per 2.7 ppb NO₂). All other associations were consistent with no effect.

These results are not indicative of large adverse associations between traffic-related air pollution exposures and indicators of neural atrophy or cerebrovascular pathology.