Mortality risk associated with heatwave exposure based on daily maximum, minimum, and combined temperature thresholds

Area of Science:

• Environmental Epidemiology
• Public Health
• Climate Change Adaptation

Background:

• Previous studies on heatwave mortality often used daily mean temperature, neglecting distinct daytime and nighttime heat effects.
• Understanding the specific impacts of different heatwave types is crucial for targeted public health interventions.

Purpose of the Study:

• To assess the association between different heatwave definitions (daily maximum, daily minimum, combined temperatures) and mortality.
• To investigate the differential impact of daytime versus nighttime heat exposure on mortality risks.

Main Methods:

• Utilized individual mortality records and residential exposure data (temperature, humidity, ozone) from 2016-2022 in Chongqing, China.
• Employed a time-stratified case-crossover design to analyze 17,552 deaths during heatwave events.
• Categorized heatwaves based on daily maximum temperature, daily minimum temperature, and combined thresholds.

Main Results:

• Heatwaves defined by combined temperature thresholds showed the highest mortality risks (ORs 1.08-1.32).
• Daily minimum temperature-defined heatwaves also indicated significant mortality risks (ORs 1.04-1.27).
• Heatwave exposure increased all-cause and cardiovascular mortality, with stronger associations observed in men and under higher ozone levels.

Conclusions:

• Compound heatwaves, encompassing both daytime and nighttime heat, pose the most significant mortality risks.
• Nighttime heat exposure is a critical factor in heatwave-related mortality and should not be underestimated.
• Findings emphasize the need to incorporate nighttime temperature monitoring and mitigation strategies into public health planning.