Europe is the continent experiencing the greatest warming, up to 1°C above the global average. © Adobe Stock

The summer of 2022 was the hottest ever recorded in Europe, characterized by an intense series of heatwaves that beat records of temperature, drought, and forest fires. Although Eurostat had already reported unusually high excess mortality for these dates, the fraction of mortality that could be attributed to the heat had not until now been quantified. And this is precisely what a study by scientists from Inserm and the Barcelona Institute for Global Health (ISGlobal) set out to do. Their analysis estimates that between May 30 and September 4, 2022 there had been 61,672 heat-related deaths in Europe. These findings suggest that our current strategies for adapting to heatwaves may still be insufficient. The full study has been published in Nature Medicine.

In 2003, Europe experienced one of the most intense heatwaves in its history, causing over 70,000 deaths. Since then, adaptation strategies have been developed in an attempt to respond quickly to intense heat and protect the most vulnerable populations. Given the continuous increase in heatwave episodes in recent years and the estimations that they could double in number by 2050, it is crucial to better characterize the mortality associated with them and evaluate the efficacy of the strategies put in place.

With the summer of 2022 being the hottest ever recorded in Europe, scientists from Inserm at the France Cohorts JSU[1] and the Barcelona Institute for Global Health looked at the number of heat-related deaths for this period.

The research team obtained temperature and mortality data for the 2015-2022 period in 823 regions of 35 European countries, representing a total population of over 543 million people. These data were used to estimate epidemiological models to predict heat-related mortality for each region and week of the summer period.

The records first revealed that the temperatures were above average throughout all the weeks of the summer period. The largest heat-related abnormality was recorded between July 11 and August 14, during which, according to the researchers, 38,881 deaths were caused by the heat. In this period, there was a particularly intense pan-European heatwave between July 18 and 24, for which a total of 11,637 deaths were attributed to the excess heat. All in all, the analysis reveals that between May 30 and September 4, 2022 there would have been 61,672 heat-related deaths in Europe.

France is the country that recorded the greatest increase in temperature compared with the seasonal averages, with +2.43ºC above the average values for 1991-2020, followed by Switzerland (+2.30ºC), Italy (+2.28°C), Hungary (+2.13ºC) and Spain (+2.11ºC).

Analyses by Country, Age and Sex

Based on the epidemiological models they built, incorporating data on temperature and number of deaths[2], the scientists were also able to propose a country-specific analysis. They showed in absolute terms that the country with the largest number of heat-related deaths throughout the summer of 2022 was Italy, with a total of 18,010 deaths, followed by Spain (11,324), and Germany (8,173). France comes in 4th place with 4,807 heat-related deaths[3].

Beyond the estimated number of heat-related deaths, the study also included an analysis based on age and sex. At European level, the results highlight a very marked increase in mortality in the upper age groups, with the vast majority of deaths concentrated in the age range of 80 and over.

For the sex-based analysis, the data show that heat-related premature mortality was 63% higher in women than in men. This increased vulnerability of women to heat is observed in the general population and above all among the over-80s, where the mortality rate is 27% higher than that of men. In contrast, the male mortality rate is 41% higher among those under 65 and 13% higher between the ages of 65 and 79.

For the research team, these findings should encourage us to take action to implement more robust preventive and protective measures. Indeed, the fact that many countries already had active prevention plans, unlike in 2003, suggests that the adaptation strategies available to us today may still be insufficient.

“The acceleration of warming observed over the past ten years underlines the urgency of in-depth re-evaluation and reinforcement of prevention plans, paying particular attention to the differences between European countries and regions, as well as between age and sex, which currently mark the differences in vulnerability to heat,” explains Hicham Achebak, Inserm researcher and last author of the study.

Europe is the continent with the highest level of warming, up to 1°C more than the world average. In this context, the team’s estimates also suggest that in the absence of an effective adaptive response, the continent will face an average of over 68,000 excess deaths each summer by 2030 and over 94,000 by 2040.

[1] The France Cohorts Joint Service Unit (JSU) brings together several academic supervisory bodies, including Inserm, Ined, Université Paris-Saclay, Université Paris Cité, and Sorbonne Université. Its long-term objective is to offer a range of services for epidemiological cohorts.

[2] The mortality data were obtained via Eurostat and the temperature data via ERA5-land reanalysis.

[3] This study focuses on heat-related mortality during the summer of 2022 using weekly data and estimated nearly 5,000 deaths in France. On the other hand, Santé Publique France has recently used daily data for the same period and estimated nearly 7,000 deaths. This difference is due to the fact that the weekly data generally underestimate the impact of heat on mortality.

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