Background

Evidence for the association between long-term exposure to ozone (O₃) and cause-specific cardiovascular disease (CVD) mortality is inconclusive, and this association has rarely been evaluated at high O₃ concentrations.

Objectives

We aim to evaluate the associations between long-term O₃ exposure and cause-specific CVD mortality in a Chinese population.

Methods

From 2009 to 2018, 744,882 subjects (median follow-up of 7.72 years) were included in the CHinese Electronic health Records Research in Yinzhou (CHERRY) study. The annual average concentrations of O₃ and fine particulate matter (PM_2.5), which were estimated using grids with a resolution up to 1 × 1 km, were assigned to the community address for each subject. The outcomes were deaths from CVD, ischemic heart disease (IHD), myocardial infarction (MI), stroke, and hemorrhagic/ischemic stroke. Time-varying Cox model adjusted for PM_2.5 and individual-level covariates was used.

Results

The mean of annual average O₃ concentrations was 68.05 μg/m³. The adjusted hazard ratio per 10 μg/m³ O₃ increase was 1.22 (95% confidence interval [CI]: 1.13–1.33) for overall CVD mortality, 1.08 (0.91–1.29) for IHD, 1.21 (0.90–1.63) for MI, 1.28 (1.15–1.43) for overall stroke, 1.39 (1.16–1.67) for hemorrhagic stroke and 1.22 (1.00–1.49) for ischemic stroke, respectively. The study showed that subjects without hypertension had a higher risk for CVD mortality associated with long-term O₃ exposure (1.66 vs. 1.15, p = 0.01).

Conclusions

We observed the association between long-term exposure to high O₃ concentrations and cause-specific CVD mortality in China, independent of PM_2.5 and other CVD risk factors. This suggested an urgent need to control O₃ pollution, especially in developing countries.