The impact of particulate matter air pollution (PM2.5) on atherosclerosis in modernizing China: a report from the CATHAY study

Background: Air pollution has been associated with an increase in cardiovascular diseases incidence. To evaluate whether air pollution can accelerate atherogenic processes, we assessed the effects of air pollution on important surrogate markers of atherosclerosis [brachial flow-mediated dilation (FMD) and carotid intima-media thickness (IMT)]. Methods: A total of 1656 Han Chinese (mean age 46.0+ 11.2 years; male 47%) in Hong Kong, Macau, Pun Yu, Yu County and the 3-Gorges Territories (Yangtze River) were studied between 1996 and 2007 [Chinese Atherosclerosis in the Aged and Young Project (the CATHAY Study)]. Cardiovascular risk profiles were evaluated. Particulate matter with an aerodynamic diameter <2.5 mu m (PM2.5) parameters were computed from satellite sensors. Brachial FMD and carotid I MT were measured by ultrasound. Results: Health parameters [age, gender, body mass index, waist : hip ratio (WHR) and glucose)] were similar in lowest and highest PM2.5 exposure tertiles, systolic and diastolic blood pressures and triglycerides were higher (P<0.001) and low-density cholesterol (LDL-C) was lower in the top PM2.5 tertile (P<0.001). Brachial FMD [7.841.77, 95% confidence interval (CI) 7.59-8.10%, vs 8.50 +/- 2.52, 95% CI 8.23-8.77%, P<0.0001) was significantly lower and carotid IMT (0.68 +/- 0.13mm, 95% CI 0.67-0.69mm vs 0.63mm +/- 0.15mm 95% CI 0.62-0.64mm; P<0.0001) was significantly thicker in the top PM2.5 tertile compared with the lowest tertile. On multiple regression, FMD was inversely related to PM2.5 (beta=0.134, P=0.015) independent of gender, age and blood pressure (model R-2 = 0.156, F-value=7.6, P<0.0001). Carotid IMT was significantly correlated with PM2.5 exposure (beta=0.381, P<0.0001) independent of age, location, gender, WHR, blood pressure and LDL-C (model R-2 = 0.408, F-value=51.4, P-value <0.0001). Conclusions: Air pollution is strongly associated with markers of early atherosclerosis, suggesting a potential target for preventive intervention.