Heat and health

Global heat-related mortality for populations older than 65 years. Source: Watts et al., 2020

Health issues

Projected increases in average temperature and in frequency, intensity and duration of heat-waves are likely to have serious impacts on public health in the WHO European Region, particularly among elderly people and in cities due to the urban heat island effect. Globally, during the past 20 years, heat-related mortality in people older than 65 years has nearly doubled, and reached about 300 000 deaths in 2018. Deaths in the WHO European Region have increased by more than 30% over the same period (Watts et al., 2020).

Age, pre-existing medical conditions and social deprivation are key factors that make people likely to experience more adverse health outcomes related to heat and extreme temperatures (WHO Regional Office for Europe, 2018). Other vulnerable groups at greater risk include people with chronic conditions (such as cardiorespiratory diseases, endocrine system disorders, mental health disorders, metabolic disorders and kidney disorders), pregnant women, small children, outdoor workers, people living in urban settings in socially and economically deprived environments, migrants and travellers. In addition to climate change, population ageing and urbanization strongly affect the relationship between temperatures and health in the WHO European Region (WHO Regional Office for Europe, 2021).

Observed effects

The potential for hazardous exposure to extreme heat has been increasing in recent decades (EEA, 2017). Heat exposure can have direct effects such as heat stress or dehydration, or indirect effects such as a worsening of cardiovascular and respiratory diseases, kidney diseases or electrolyte disorders. The direct effects of heat mostly occur on the same day and in the following 3 days (WHO Regional Office for Europe, 2018). Globally, vulnerable populations experienced 475 million additional exposures to heat-wave events in 2019, which was, in turn, reflected in excess morbidity and mortality (Watts et al., 2020). In 2018, the monetized cost of heat-related mortality in the WHO European Region was equivalent to the average income of 11 million Europeans (Watts et al., 2020). City-specific studies showed a reduction in heat mortality in Mediterranean cities but not in cities in the north of the Region (WHO Regional Office for Europe, 2021).

Projected effects

The projections for Europe indicate that the number of days with high heat stress levels will be increasing everywhere in the region (EEA, 2017), while heat-related impacts could increase substantially through the combined effects of climate change, urbanization and ageing. In the last decade, a number of scientific studies have provided projections of heat-related health impacts for the WHO European Region at local, subnational and national levels. Accordingly, the heat-wave probability has increased for 31 European capitals, while all European metropolitan areas will be more vulnerable to extreme heat in the coming decades (WHO Regional Office for Europe, 2021). The magnitude of the heat effects on human health depends on future emissions of greenhouse gases as well as the extent of preventive measures introduced around the world. The European Union could experience over 100 000 additional annual heat fatalities by the end of the century under a high warming scenario. The number of fatalities would be much less if the global temperature rise was limited to 2°C. Thus, limiting warming to below 2°C could prevent mortality and morbidity associated with heat (EASAC, 2019). Without high levels of adaptation, climate change is bound to increase the heat-related burden of disease substantially.

Policy responses

Heat prevention requires a portfolio of actions at different levels, including meteorological early warning systems, timely public and medical advice, improvements to housing and urban planning, and ensuring that health-care and social systems are ready to act. These actions can be integrated into a systematic public health response – a heat–health action plan (HHAP). Countries are at different stages of preparing, developing and implementing HHAPs. The WHO Regional Office for Europe conducted a survey in 2019, which looked into governance and institutional arrangements for HHAPs. Of a total of 35 countries participating in the survey, 16 indicated the existence of a national HHAP, with several more countries having established HHAPs at subnational or city level (WHO Regional Office for Europe, 2021).

The Observatory page on National heat-health action plans and warning systems provides an overview of national (and some subnational) heat-health action plans and warning systems. Further resources on improving the capacity to protect populations from the avoidable health risks of extreme heat in our changing climate are provided by the Global Heat Health Information Network, which is coordinated by the WHO/WMO Joint Office for Climate and Health.


Links to further information