The effect of heatwave and cold spell on cardiovascular disease mortality in central China, 2018-2022.

Unlabelled: Heatwave and cold spell have been linked to cardiovascular disease (CVD) mortality. However, due to the varying definitions of heatwave and cold spell, their impacts on CVD mortality are inconsistent.

Methods: A time series study in Hunan province, central of China, from 2018 to 2022, was conducted to test the relationship between heatwave, cold spell and CVD mortality. According to different percentiles of daily mean temperatures and exposure duration, we built 9 kind of definitions for heatwave and cold spell. Distributed lag non-linear model was used to analyze the associations between heatwave, cold spell and CVD mortality, and the attributable fraction (AF) were estimated.

Results: The relative risks of CVD mortality associated with heatwave and cold spell varied depending on the definitions, ranging from 1.154 (95% CI: 1.148-1.160) to 1.229 (95% CI: 1.215-1.243) for heatwaves, and from 1.196 (95% CI: 1.192-1.201) to 1.290 (95% CI: 1.282-1.297) for cold spells. Under the definition of 95th percentile with ≥ 4-d duration (P95_4d), the total AF of CVD mortality attributable to heatwave was the largest at 8.43 (95% CI: 7.92-8.94). For the definition of 5th percentile with ≥ 3-d duration (P5_3d), the total AF attributable to cold spell was the largest at 12.96 (95% CI: 12.64-13.28). For heatwave and cold spell, higher CVD mortality risks were observed in females and the elderly over 75 years than males and young people.

Discussion: We found that both heatwave and cold spell could increase the mortality risk of CVD. The results highlight the importance of implementing warning systems for extreme temperature.