Increased respiration during physical activity may increase air pollution dose, which may attenuate the benefits of physical activity on cardiovascular disease (CVD) risk and overall mortality.
We aimed to examine the multiplicative interaction between long-term ambient residential exposure to fine particulate matter () and physical activity in the association with CVD risk and overall mortality.
We followed 104,990 female participants of the U.S.-based prospective Nurses' Health Study from 1988 to 2008. We used Cox proportional hazards models to assess the independent associations of 24-months moving average residential exposure and physical activity updated every 4 y and the multiplicative interaction of the two on CVD (myocardial infarction and stroke) risk and overall mortality, after adjusting for demographics and CVD risk factors.
During 20 years of follow-up, we documented 6,074 incident CVD cases and 9,827 deaths. In fully adjusted models, exposure was associated with modest increased risks of CVD [hazard ratio (HR) for fifth quintile compared to first quintile : 1.09, 95% confidence interval (CI): 0.99, 1.20; ] and overall mortality (HR fifth compared to first quintile: 1.10, 95% CI: 1.02, 1.19; ). Higher overall physical activity was associated with substantially lower risk of CVD [HR fourth quartile, which was equivalent of task (MET)-h/wk, compared to first quartile (): 0.61, 95% CI: 0.57, 0.66; ] and overall mortality (HR fourth compared to first quartile: 0.40, 95% CI: 0.37, 0.42; ). We observed no statistically significant interactions between exposure and physical activity (overall, walking, vigorous activity) in association with CVD risk and overall mortality.
In this study of U.S. women, we observed no multiplicative interaction between long-term exposure and physical activity; higher physical activity was strongly associated with lower CVD risk and overall mortality at all levels of exposure. https://doi.org/10.1289/EHP7402.