Heat and health
### Key Facts:
- **Heat as a Hazard**: Heat is a significant environmental and occupational health risk. It is the leading cause of weather-related deaths and can worsen underlying health conditions, including cardiovascular disease, diabetes, mental health disorders, asthma, and can increase the risk of accidents and transmission of infectious diseases. Heatstroke, in particular, is a medical emergency with a high fatality rate.
- **Growing Exposure**: The number of people exposed to extreme heat is rising rapidly due to climate change across all regions. Heat-related deaths among people over 65 years old increased by approximately 85% between 2000–2004 and 2017–2021. Studies estimate that around 489,000 heat-related deaths occur annually worldwide, with the majority in Asia and Europe. High-intensity heatwaves, such as those in Europe in 2003 and Russia in 2010, have caused tens of thousands of deaths.
- **Vulnerability Factors**: Vulnerability to heat is influenced by both physiological factors, like age and health status, and exposure factors such as occupation and socio-economic conditions.
- **Preventability**: The health impacts of heat are largely predictable and preventable through targeted public health and multi-sectoral interventions. WHO provides guidance for managing extreme heat risks, emphasizing that action on climate change and comprehensive preparedness can save lives.
### Overview:
- **Heatwaves**: Defined as periods of local excess heat over several unusually hot days and nights, heatwaves are becoming more frequent, longer, and more intense due to climate change. This trend is expected to continue, leading to more health risks.
- **Impact on Health**: Heatwaves can cause rapid increases in illness and death, especially in vulnerable populations such as the elderly, those with chronic illnesses, and those without access to cooling. The urban heat island effect, exacerbated by poor city planning and lack of green spaces, also contributes to increased heat exposure.
- **Challenges**: Awareness among health workers and the public about the dangers of heat is still lacking. Health systems need to adjust their planning and interventions to address increasing heat exposures effectively.
### Who is Affected?
- **Vulnerable Populations**: This includes people in tropical and subtropical climates who are chronically exposed to high temperatures, outdoor and manual workers, athletes, and those living in poor-quality housing. Gender also plays a role, with women sometimes more exposed due to responsibilities like cooking indoors during hot weather.
### How Does Heat Impact Health?
- **Heat Storage in the Body**: Heat stress occurs when the body cannot eliminate internally generated heat due to environmental factors, clothing, or direct heat gain from the environment. This can lead to heat exhaustion or heatstroke, and exacerbate chronic health conditions like cardiovascular disease and diabetes.
- **Rapid Onset**: Deaths and hospitalizations due to extreme heat often occur quickly, requiring immediate public health interventions.
### Public Action:
- **Staying Cool**: Recommendations include avoiding outdoor activities during the hottest parts of the day, staying in cool places, and staying hydrated. Specific advice is given for keeping homes cool, protecting vulnerable individuals, and keeping infants and children safe from heat.
### WHO Response:
- **Climate Action**: WHO emphasizes the urgent need to mitigate climate change by reducing greenhouse gas emissions. They also work with health sectors to prepare for and respond to the health impacts of heatwaves by developing heat action plans and early warning systems.
- **Collaboration**: WHO collaborates with various organizations, including the Global Heat Health Information Network and the World Meteorological Organization, to share knowledge and develop strategies to address extreme heat.
### References:
- Lancet Countdown: Heat-related Mortality. 2023.
- Zhao et al, 2021 Global, regional, and national burden of mortality associated with non-optimal ambient temperatures from 2000 to 2019.
- Heat-related mortality in Europe during the summer of 2022.
- Hot weather and heat extremes: health risks. The Lancet.
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