Background: 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.
Objectives: 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.
Methods: 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.
Results: 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.
Discussion: 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.