Long-Term Ambient Air Pollution Exposures and Brain Imaging Markers in Korean Adults: The Environmental Pollution-Induced Neurological EFfects (EPINEF) Study

BACKGROUND: Only a limited number of neuroimaging studies have explored the effects of ambient air pollution in adults. The prior studies have investigated only cortical volume, and they have reported mixed findings, particularly for gray matter. Furthermore, the association between nitrogen dioxide (NO2) and neuroimaging markers has been little studied in adults. OBJECTIVES: We investigated the association between long-term exposure to air pollutants (NO2, particulate matter (PM) with aerodynamic diameters of <= 10 lm (PM10) and <= 2.5 mu m (PM2.5), and neuroimaging markers. METHODS: The study included 427 men and 530 women dwelling in four cities in the Republic of Korea. Long-term concentrations of PM10, NO2, and PM2.5 at residential addresses were estimated. Neuroimaging markers (cortical thickness and subcortical volume) were obtained from brain magnetic resonance images. A generalized linear model was used, adjusting for potential confounders. RESULTS: A 10-lg/m3 increase in PM10 was associated with reduced thicknesses in the frontal [-0.02 mm (95% CI: -0.03, -0.01)] and temporal lobes [-0.06 mm (95% CI: -0.07, -0.04)]. A 10-lg/m3 increase in PM2.5 was associated with a thinner temporal cortex [-0.18 mm (95% CI: -0.27, - 0.08)]. A 10-ppb increase in NO2 was associated with reduced thicknesses in the global [-0.01 mm (95% CI: -0.01, 0.00)], frontal [-0.02 mm (95% CI: -0.03, -0.01)], parietal [-0.02 mm (95% CI: -0.03, -0.01)], temporal [-0.04 mm (95% CI: -0.05, -0.03)], and insular lobes [-0.01 mm (95% CI: - 0.02, 0.00)]. The air pollutants were also associated with increased thicknesses in the occipital and cingulate lobes. Subcortical structures associated with the air pollutants included the thalamus, caudate, pallidum, hippocampus, amygdala, and nucleus accumbens. DISCUSSION: The findings suggest that long-term exposure to high ambient air pollution may lead to cortical thinning and reduced subcortical volume in adults.