Long-term exposure to ozone and cardiovascular mortality in a large Chinese cohort

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.

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

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.

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).

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.