Long-Term Ambient Ozone Exposure and Incident Cardiovascular Diseases: National Cohort Evidence in China

Background Long-term ozone exposure has been associated with cardiovascular disease (CVD) mortality in mounting cohort evidence, yet its relationship with incident CVD was poorly understood, especially in low- and middle-income countries (LMICs) experiencing high ambient air pollution. Methods We carried out a nationwide perspective cohort study from 2010 through 2018 by dynamically enrolling 36985 participates across Chinese mainland. Warm-season (April–September) ozone concentrations were estimated using satellite-based machine-learning models with national coverage. Cox proportional hazards model with time-varying exposures was employed to evaluate the association of long-term ozone exposure with incident CVD (overall CVD, hypertension, stroke, and coronary heart disease [CHD]). Assuming causality, a counterfactual framework was employed to estimate ozone-attributable CVD burden based on the exposure-response (E-R) relationship obtained from this study. Decomposition analysis was utilized to quantify the contributions of four key direct driving factors (ozone exposure, population size, age structure, and incidence rate) to the net change of ozone-related CVD cases between 2010 and 2018. Results A total of 4428 CVD, 2600 hypertension, 1174 stroke, and 337 CHD events were reported during 9-year follow-up. Each 10-μg/m³ increase in warm-season ozone was associated with an incident risk of 1.078 (95% confidence interval [CI]:1.050–1.106) for overall CVD, 1.098 (95% CI:1.062–1.135) for hypertension, 1.073 (95% CI:1.019–1.131) for stroke, and 1.150 (95% CI: 1.038–1.274) for CHD, respectively. We observed no departure from linear E-R relationships of ozone exposure with overall CVD (Pnonlinear= 0.22), hypertension (Pnonlinear=0.19), stroke (Pnonlinear= 0.70), and CHD (Pnonlinear= 0.44) at a broad concentration range of 60–160µg/m3. Compared with rural dwellers, those residing in urban areas were at significantly greater ozone-associated incident risks of overall CVD, hypertension, and stroke. We estimated 1.22 million (10.6% of overall CVD in 2018) incident CVD cases could be attributable to ambient ozone pollution in 2018, representing an overall 40.9% growth (0.36 million) compared to 2010 (0.87 million, 9.7% of overall CVD in 2010). This remarkable rise in ozone-attributable CVD cases was primary driven by population aging (+24.0%), followed by increase in ozone concentration (+10.5) and population size (+6.7%). Conclusions Long-term ozone exposure was associated with an elevated risk and burden of incident CVD in Chinese adults, especially among urban dwellers. Our findings underscored policy priorities of implementing joint control measures for fine particulate matter and ozone in the context of accelerated urbanization and population aging in China. Environmental Implication This study well depicted spatiotemporal patterns of O3-attributable CVD burden in Chinese mainland and quantify underlying driving factors, which would facilitate dynamic assessments of ozone-related health impacts and development of region-specific ozone policies in China.