Evidence linking air pollution and blood pressure mediated by body weight in China

Air pollution is continuing to be at a high level in China, which may lead to an increased risk of obesity and hypertension. In the study, we aimed to examine the association between air pollution and prevalence of hypertension and tested whether this air pollution and hypertension association was mediated by changes in body weight. We used a linkage dataset from China with nationwide city-level air quality data linked with individual-level health data from the China Health and Retirement Longitudinal Study among adults aged 45 or older. Air quality was assessed based on the daily air quality index (AQI), a standard sum index of multiple air pollutants. To be specific, air pollution was measured by number of polluted days according to AQI and monthly average AQI. We examined the association between air quality and hypertension and tested mediation effect of body weight using a four-step mediating regression model. Air pollution was a risk factor for obesity. Each exposure to one more polluted day for females predicted on 2.1% (OR 1.021; 95% CI 1.007-1.035) higher prevalence of hypertension without BMI adjusted. A significant mediation effect of body mass index on the association between AQI and hypertension was observed. However, the effect of air pollution on hypertension among males was not significant. These results provide further evidence of the potential risks of air pollution and suggest that reducing pollution could help control both obesity and blood pressure.