Supplementary Material for: Effects of ambient air pollution on brain cortical thickness and subcortical volume: A longitudinal neuroimaging study

Introduction: Long-term exposure to air pollutants is associated with an increased risk of Alzheimer’s disease and mild cognitive impairment. Therefore, we investigated the association between long-term air pollution exposure and changes in neuroimaging markers.
Methods: In this longitudinal study, we studied 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.
Results: A 10-μg/m3 increase in PM10 was associated with reduced whole-brain mean (β= -0.45, standard error (SE)= 0.10, P< 0.001), frontal (β= -0.53, SE= 0.11; P< 0.001) and temporal thicknesses (β= -0.37, SE= 0.12; P= 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; P< 0.001), frontal (β= -0.25, SE= 0.05; P< 0.001), parietal (β= -0.12, SE= 0.05; P= 0.025), and temporal thicknesses (β= -0.19, SE= 0.06; P= 0.001). Subcortical structures associated with air pollutants include the thalamus volume.
Conclusions: Long-term exposure to PM10 and NO2 may lead to cortical thinning in adults.