Impact of Obesity and Ozone on the Association Between Particulate Air Pollution and Cardiovascular Disease and Stroke Mortality Among US Adults

BACKGROUND: Cardiovascular diseases (CVDs) and stroke are the highest and third highest causes of death, respectively, in the whole United States. It is well established that both long‐ and short‐term exposure to particulate air pollution (particulate matter with diameters <2.5 μm [PM (2.5)]) increases the risks of both CVD and stroke mortality. METHODS AND RESULTS: We combined county‐level data for CVD and stroke mortality, and prevalence of hypertension and obesity, with spatial patterns of PM (2.5) and ozone in a cross‐sectional ecological study. We found significant positive associations between both CVD (β=15.4, P<0.001) and stroke (β=2.7, P<0.001) mortality with PM (2.5). Ozone had significant link with just CVD (β=1372.1, P<0.001). Once poverty, ethnicity, and education were taken into account, there were still significant positive associations between PM (2.5) and both CVD (β=1.2, P<0.001) and stroke (β=1.1, P<0.001) mortality. Moreover, the association between CVD and ozone remained after adjustment for these factors (β=21.8, P<0.001). PM (2.5) and ozone were independent risk factors. The impact of PM (2.5) on CVD and stroke mortality was strongly dependent on the prevalence of obesity. Hypertension partially mediated the associations of PM (2.5) and mortality from CVD and stroke. CONCLUSIONS: There was a spatial association between PM (2.5) exposure and the leading causes of death and disability in United States. The effect of PM (2.5) was considerably greater in areas where obesity is more prevalent. Hypertension is a possible mediator of the association of PM (2.5) and both CVD and stroke.