Widowhood disparities in nonaccidental mortality attributable to heat waves and ozone

Emerging evidence suggests that heat waves and ozone (O₃) contribute to increased mortality risks. Since widowhood is a common event that can increase individuals' susceptibility to the environment, it is of great importance and interest to elucidate the widowhood disparity in mortality attributable to heat waves and O₃. We therefore conducted a case-crossover study of 1,214,763 nonaccidental deaths in Jiangsu Province, China, during 2015-2021 to investigate the independent and interactive associations of exposure to heat waves and O₃ with mortality by widowhood status. Grid-level heat waves were defined by multiple combinations of apparent temperature thresholds and durations. Residential heat waves and O₃ exposures were assessed using validated grid datasets. Conditional logistic regression models were applied for exposure-response analyses and evaluations of additive interactions. Exposure to heat waves and O₃ was significantly associated with increased odds of mortality in both widowed (odds ratio for heat waves, 1.25; O₃, 1.06 per interquartile range increase) and married subjects (1.08; 1.03), and these associations were higher in widowed subjects. A significant synergistic interaction was observed between heat waves and O₃, which was stronger in widowed subjects (relative excess odds due to interaction, 0.14 vs. 0.03). Up to 6.43% and 3.56% of deaths were attributable to heat waves, O₃ pollution, and their compound events in widowed and married subjects, respectively. Our findings suggest that widowed individuals are more susceptible to heat waves and O₃ and highlight the need to consider differences associated with widowhood disparities in preventing premature deaths due to heat waves and O₃ exposures.