Overweight modifies the association between long-term ambient air pollution and prehypertension in Chinese adults: the 33 Communities Chinese Health Study

Background: Research regarding the interaction of ambient air pollution and overweight on prehypertension is scarce. We aimed to test whether overweight modifies the association between long-term exposure to ambient air pollution and prehypertension in Chinese adults. Methods: A total of 16,188 Chinese adults, aged 18-74 years old, from 33 communities in 3 Northeastern Chinese cities were evaluated. Three year average levels of particles with an aerodynamic diameter <= 10 mu m (PM10), sulfur dioxides (SO2), nitrogen dioxides (NO2), and ozone (O-3) were calculated at monitoring stations. Generalized additive models and 2-level regression analyses were applied. Results: We observed significant interactions between air pollutants and overweight on prehypertension and blood pressure. The associations of PM10, SO2, NO2, and O-3 with prehypertension were significant among overweight participants (Prevalence Rate Ratios (PRRs) per interquartile range (IQR) of air pollutants: 1.14-1.20), but not among normal weight participants (PRRs: 0.98-1.04). PM10, SO2, and O-3 were significantly associated with systolic blood pressure (SBP), and the magnitudes of these associations were higher among overweight adults (increases in SBP per IQR of air pollutants: 1. 82-4.53 mmHg) than those among normal weight adults (increases in SBP: 0.42-0.61 mmHg). For diastolic blood pressure (DBP), significant associations were mainly observed in overweight participants (increases in DBP: 0.80-1.63 mmHg). Further stratified analyses showed that all these interactions were stronger in women, the older, and participants living in areas with lower income levels or higher population density. Conclusions: Being overweight may enhance the effects of ambient air pollution on prehypertension and blood pressure in Chinese adults.