Heat-related deaths
High temperatures and heatwaves pose a threat to human health. Heat can lead to exhaustion and heat stroke. It can also exacerbate existing conditions such cardiovascular and respiratory diseases, kidney problems or mental health issues. According to the European Environment Agency EEA, heat is the greatest direct climate-related threat to human health in Europe.
The «heat-related deaths» indicator estimates the number of deaths statistically attributable to heat stress in Switzerland between May and September. The indicator can be used to track the long-term impacts of climate change on human health and determine the need for adaptation measures.
poor
unsatisfactory
The largest number of heat-related deaths in the period 1980-2023 is estimated for the warmest summer to date (2003). In the record summer of 2003, a total of 1,402 deaths (95% confidence interval (CI): 1,157-1,658) were attributed to the heat. This corresponds to a 5.6% share of total mortality between May and September. In summer 2023, the fifth warmest summer to date, 542 (95% confidence interval CI: 364-715) deaths are attributed to the heat. This corresponds to 2.0% (95% CI: 1.3%-2.6%) of all deaths in the warm season between May and September. The mortality rate associated with heat was 6.0 (95% CI: 4.1-8.0) deaths per 100,000 inhabitants (p.e.). This is the third-highest figure since the summer of 2003. The 75+ age group is generally the most affected and the proportion of annual heat-related deaths is higher among women than men.
To assess the effects of different daily average temperatures, the heat-related deaths are shown for three temperature ranges according to the threshold values for heat warnings issued by MeteoSwiss. Most heat-related deaths are attributable to moderately hot (above the year-specific optimum temperature and below 25°C) and hot daily average temperatures (above 25°C and below 27°C). Although the risk of heat-related deaths is lower on such days than on very hot days (above 27°C), they occur much more frequently.
The annual number of heat-related deaths did not increase between 1980 and 2023 in line with the rising average summer temperature in Switzerland. The heat-related mortality rate per 100,000 p.e. in 2023 is lower than for hot summers at the beginning of the time series. The impact on mortality is lower today than in the past, especially on days with moderately hot mean daily temperatures. This observation indicates that society has partially adapted to the increasing heat stress.
The impact indicator "Heat-related deaths" shows a clear effect of heat on mortality. Particularly on days with hot (from 25°C) and very hot (from 27°C) average daily temperatures, significant increases in heat-related deaths are observed. Due to the high number of heat-related deaths in 2023, the current status of the indicator is rated as "poor". Heat waves and hot days are increasing in frequency and intensity with climate change. Measures to protect the population are therefore of great importance. The development of the indicator is therefore assessed as "unsatisfactory".
Further information on "Heat and health" from the National Centre for Climate Services: Human Health (admin.ch).
There is currently no uniform international reporting on heat-related mortality, so it is not possible to make comparisons at international level on the basis of this indicator.
Since 2023, the heat-related death rate in Switzerland have been estimated based on the number of deaths attributable to heat-related causes. Data on the measured mean daily temperatures is associated with exposure and outcome data to show the correlation between temperature and observed mortality. Unlike the current mortality statistics of the FSO and the the analyses of excess mortality in especially hot summers, the «heat-related deaths» indicator incorporates the temperature measures by MeteoSchweiz. This better takes into account the impact of moderately hot and warmer periods. The method can also attribute deaths to heat-related causes if several extraordinary events simultaneously exert an influence on mortality in one summer. The indicator thus complements the FSO's Mortality statistics, which compares weekly numbers of deaths against expected mortality.
Explanation of daily mean temperatures: A daily mean temperature of 25°C is reached, for example, when the daily minimum temperature is 21°C and the maximum is 29°C, or when the daily minimum is 18°C and the maximum is 32°C. Very hot conditions of more than 27°C daily mean are reached, for example, with a combination of 15.9°C daily minimum and 36.5°C daily maximum or 22.2°C daily minimum and 32.3°C daily maximum.
Monitoring «Hitzebedingte Todesfälle» 2000 bis 2022, Bericht des SwissTPH im Auftrag von BAFU und BAG, 2023 (PDF, 2 MB, 02.08.2023) (available in German)
Monitoring «Monitoring hitzebedingte Todesfälle: Sommer 2023, Bericht des SwissTPH im Auftrag von BAFU und BAG, 2024» (available in German)
Further information
