To Save Lives in Heatwaves, Focus on How Human Bodies Work
In our recent Nature article, we argue that heat-health preparedness should prioritize cooling people, not just the air. With tens of thousands of heat-related deaths each year and rising global temperatures, current public health strategies relying on air temperature thresholds are not enough. Instead, we propose a physiology-based approach that integrates individual and environmental factors to assess and reduce heat-health risk.
Extreme heat affects not only mortality but also mental health, pregnancy outcomes, learning, and workplace productivity. Traditional warnings based on air temperature miss critical factors like humidity, radiant heat, wind, clothing, activity, age, and health status. Our research demonstrates that personalized physiological models can better predict risk and guide effective, sustainable cooling interventions.
Key Findings
- Heat stress is multi-factorial: Risk depends on more than air temperature—radiation, humidity, wind, clothing, activity, age, and health all matter.
- Physiology-based models outperform temperature-only warnings: By integrating personal and environmental data, we can estimate core temperature, dehydration, and cardiac strain for individuals.
- HeatWatch tool: We developed a free online tool that provides personalized heat-health risk forecasts and tailored cooling advice using a six-point risk scale.
- Cooling people is more sustainable than cooling spaces: Strategies like moving air with fans, increasing shade, and wetting skin can reduce physiological strain without excessive energy use.
- Targeted interventions: Physiology-based risk assessment enables more effective deployment of resources (e.g., cooling hubs) and supports vulnerable groups.
Practical Recommendations
- Use personalized heat-health risk tools (like HeatWatch) to guide protective actions during heatwaves.
- Combine fans with air conditioning set to higher temperatures (26–27°C) to reduce energy use by up to 70% without sacrificing comfort.
- Increase access to shade and retrofit buildings to lower indoor temperatures.
- Employ sweat-mimicking strategies (e.g., wetting skin) for additional cooling, especially for older adults and those with heart disease.
- Shift public health messaging from air temperature thresholds to physiology-based risk assessment for more effective and equitable protection.
As global temperatures rise, it is time to move beyond air temperature warnings and use physiology to translate hot weather into actionable health risk.