Long-term exposure to fine particulate matter modifies the association between physical activity and hypertension incidence

BACKGROUND: The trade-off between the benefits of regular physical activity (PA) and the potentially detrimental effects of augmented exposure to air pollution in highly polluted regions remains unclear. This study aimed to examine whether ambient fine particulate matter (PM(2.5)) exposure modified the impacts of PA volume and intensity on hypertension risk. METHODS: We included 54,797 participants without hypertension at baseline in a nationwide cohort of the Prediction for Atherosclerotic Cardiovascular Disease Risk in China (China-PAR) project. PA volume and intensity were assessed by questionnaire, and high-resolution (1 km ×1 km) PM(2.5) estimates were generated using a satellite-based model. RESULTS: During 413,516 person-years of follow-up, 12,100 incident hypertension cases were identified. PM(2.5) significantly modified the relationship between PA and hypertension incidence (p(interaction) < 0.001). Increased PA volume was negatively associated with incident hypertension in the low PM(2.5) stratum (<59.8 μg/m(3), p(trend) < 0.001), with a hazard ratio of 0.81 (95% confidence interval (95%CI): 0.74–0.88) when comparing the fourth with the first quartile of PA volume. However, the health benefits were not observed in the high PM(2.5) stratum (≥59.8 μg/m(3), p(trend) = 0.370). Moreover, compared with light PA intensity, vigorous intensity was related to a 20% (95%CI: 9%–29%) decreased risk of hypertension for participants exposed to low PM(2.5), but a 17% (95%CI: 4%–33%) increased risk for those with high PM(2.5) levels. CONCLUSION: PA was associated with a reduced risk of hypertension only among participants with low PM(2.5) exposure. Our findings recommended regular PA to prevent hypertension in less polluted regions and reinforced the importance of air quality improvement.