Association between Ambient Air Pollution and MRI-Defined Brain Infarcts in Health Examinations in China

The study aimed to evaluate the relationships between air pollutants and risk of magnetic resonance imaging (MRI)-defined brain infarcts (BI). We used data from routine health examinations of 1,400,503 participants aged >= 18 years who underwent brain MRI scans in 174 cities in 30 provinces in China in 2018. We assessed exposures to particulate matter (PM)(2.5), PM10, nitrogen dioxide (NO2), and carbon monoxide (CO) from 2015 to 2017. MRI-defined BI was defined as lesions >= 3 mm in diameter. Air pollutants were associated with a higher risk of MRI-defined BI. The odds ratio (OR) (95% CI) for MRI-defined BI comparing the highest with the lowest tertiles of air pollutant concentrations was 2.00 (1.96-2.03) for PM2.5, 1.68 (1.65-1.71) for PM10, 1.58 (1.55-1.61) for NO2, and 1.57 (1.54-1.60) for CO. Each SD increase in air pollutants was associated with 16-42% increases in the risk of MRI-defined BI. The associations were stronger in the elderly subgroup. This is the largest survey to evaluate the association between air pollution and MRI-defined BI. Our findings indicate that ambient air pollution was significantly associated with a higher risk of MRI-defined BI.