Effects of Ambient Air Pollution on Brain Cortical Thickness and Subcortical Volume: A Longitudinal Neuroimaging Study

Abstract

<b><i>Introduction:</i></b> Several cross-sectional studies have shown that long-term exposures to air pollutants are associated with smaller brain cortical volume or thickness. Here, we investigated longitudinal associations of long-term air pollution exposures with cortical thickness and subcortical volume. <b><i>Methods:</i></b> In this longitudinal study, we included a prospective cohort of 361 adults residing in four cities in the Republic of Korea. Long-term concentrations of particulate matter with aerodynamic diameters of ≤10 μm (PM10) and ≤2.5 μm (PM2.5) and nitrogen dioxide (NO₂) at residential addresses were estimated. Neuroimaging markers (cortical thickness and subcortical volume) were obtained from brain magnetic resonance images at baseline (August 2014 to March 2017) and at the 3-year follow-up (until September 2020). Linear mixed-effects models were used, adjusting for covariates. <b><i>Results:</i></b> A 10-μg/m³ increase in PM10 was associated with reduced whole-brain mean (β = −0.45, standard error [SE] = 0.10; <i>p</i> &lt; 0.001), frontal (β = −0.53, SE = 0.11; <i>p</i> &lt; 0.001) and temporal thicknesses (β = −0.37, SE = 0.12; <i>p</i> = 0.002). A 10-ppb increase in NO₂ was associated with a decline in the whole-brain mean cortical thickness (β = −0.23, SE = 0.05; <i>p</i> &lt; 0.001), frontal (β = −0.25, SE = 0.05; <i>p</i> &lt; 0.001), parietal (β = −0.12, SE = 0.05; <i>p</i> = 0.025), and temporal thicknesses (β = −0.19, SE = 0.06; <i>p</i> = 0.001). Subcortical structures associated with air pollutants included the thalamus. <b><i>Conclusions:</i></b> Long-term exposures to PM10 and NO₂ may lead to cortical thinning in adults.