Heat and health

Heat is an important environmental and occupational health hazard. Heat stress is the leading cause of weather-related deaths and can exacerbate underlying illnesses including cardiovascular disease, diabetes, mental health, asthma, and can increase the risk of accidents and transmission of some infectious diseases. Heatstroke is a medical emergency with a high-case fatality rate.

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The number of people exposed to extreme heat is growing exponentially due to climate change in all world regions. Heat-related mortality for people over 65 years of age increased by approximately 85% between 2000-2004 and 2017-2021 (1).

Between 2000-2019 studies show approximately 489 000 heat-related deaths occur each year, with 45% of these in Asia and 36% in Europe (2). In Europe alone in the summer of 2022, an estimated 61 672 heat-related excess deaths occurred (3). High intensity heatwave events can bring high acute mortality; in 2003, 70 000 people in Europe died as a result of the June-August event. In 2010, 56 000 excess deaths occurred during a 44-day heatwave in the Russian Federation.

Vulnerability to heat is shaped by both physiological factors, such as age and health status, and exposure factors such as occupation and socio-economic conditions.

The negative health impacts of heat are predictable and largely preventable with specific public health and multi-sectoral policies and interventions. WHO has issued guidance for public health institutions to identify and manage extreme heat risks. Action on climate change combined with comprehensive preparedness and risk management can save lives now and in the future.

Overview

A heatwave is a period where local excess heat accumulates over a sequence of unusually hot days and nights. Heatwaves and prolonged excess heat conditions are increasing in frequency, duration, intensity and magnitude due to climate change. Even low and moderate intensity heat waves can impact the health and well-being of vulnerable populations.