Ozone, Heat Wave, and Cardiovascular Disease Mortality: A Population-Based Case-Crossover Study

A case-crossover study among 511,767 cardiovascular disease (CVD) deaths in Jiangsu province, China, during 2015-2021 was conducted to assess the association of exposure to ambient ozone (O₃) and heat wave with CVD mortality and explore their possible interactions. Heat wave was defined as extreme high temperature for at least two consecutive days. Grid-level heat waves were defined by multiple combinations of apparent temperature thresholds and durations. Residential O₃ and heat wave exposures were assessed using grid data sets (spatial resolution: 1 km × 1 km for O₃; 0.0625° × 0.0625° for heat wave). Conditional logistic regression models were applied for exposure-response analyses and evaluation of additive interactions. Under different heat wave definitions, the odds ratios (ORs) of CVD mortality associated with medium-level and high-level O₃ exposures ranged from 1.029 to 1.107 compared with low-level O₃, while the ORs for heat wave exposure ranged from 1.14 to 1.65. Significant synergistic effects on CVD mortality were observed for the O₃ and heat wave exposures, which were generally greater with higher levels of the O₃ exposure, higher temperature thresholds, and longer durations of heat wave exposure. Up to 5.8% of the CVD deaths were attributable to O₃ and heat wave. Women and older adults were more vulnerable to the exposure to O₃ and heat wave exposure. Exposure to both O₃ and heat wave was significantly associated with an increased odds of CVD mortality, and O₃ and heat wave can interact synergistically to trigger CVD deaths.