With three episodes of extreme heat waves, the summer of 2022 was the second hottest after that of 2003. The influx of patients linked to the high temperatures put hospital services to the testalready severely affected by the Covid-19 pandemic. In 2003, the heat wave that hit France from August 1 to 20 killed around 14,800 people. Was this dramatic toll repeated in 2022? On Twitter, Good friend accountbacked by a blog on global warming and followed by nearly 70,000 users, affirm that “This summer’s heat waves killed more than 10,000 people in France”. Franceinfo tried to find out if he was saying true or fake?
According to estimates, this summer’s heat waves killed more than 10,000 people in France.
Why is this figure never mentioned when the government is questioned on ecological issues? Inaction kills. The lack of information too.— Good friend (@Good friend) October 28, 2022
This figure of “10,000 dead in France” for the summer of 2022 is based on a calculation of excess mortality carried out by Insee, published at the beginning of September and updated at the end of October, which was relayed in particular by The world in an article. But can we use this figure as an estimate of the number of deaths attributable to recent heat waves?
According to INSEE documentation, between June 1 and August 31, 2022 (period corresponding to the notion of meteorological summer), “155,603 deaths have been recorded in France”. That is 13,911 additional deaths from all causes compared to the same period in 2019. Although the Institute of statistics does not establish a causal link between these deaths and the three waves of heat wave, it notes a correlation between the peaks of death and the heat wave episodes.
A first peak in deaths, on June 18, coincides with the first heat wave of the summer which lasted from June 15 to 22. The second peak in deaths, observed on July 19, coincides with the heat wave from July 12 to 25, marked by “peaks in the use of emergency care from July 15 to 18”, notes INSEE. Finally, two other peaks in deaths, on August 4 and 13, coincided with the third heat wave of the summer which “started on July 31 and ended around mid-August”.
Mortality in the summer of 2022 therefore increased by almost 10% compared to the summer of 2019, the reference year used by INSEE, because it is the last year before the Covid-19 pandemic. However, if there is a correlation between peaks in death and peaks in mortality, the INSEE data are not enough to confirm that the heat wave is responsible for all of the excess mortality observed this summer. According to data from Public Health France, a peak in deaths linked to Covid-19 was also observed the week of July 21, which also coincides with a peak in heat.
Between June 1 and August 31, Public Health France recorded 5,760 deaths linked to Covid-19. It is therefore possible to say that approximately 8,000 deaths out of the 13,911 additional deaths in the summer of 2022 are not due to the pandemic. But difficult to say that all are linked to the heat wave. “When there are several disruptive elements, we are annoyed”, explains Jean-Marie Robine, director of research at the National Institute for Health and Medical Research (Inserm) and associate researcher at the National Institute for Demographic Studies (INED). According to him, it is still too early to know the death toll due to the heat waves of the summer of 2022.
“To really disentangle the deaths linked to the heat wave, deaths linked to Covid-19, and other causes, it is necessary to carry out a precise analysis of the death certificates, which will take more time.”
Jean-Marie Robine, researcher at Inserm and INEDat franceinfo
Even with the death certificates, several problems arise in counting the deaths attributable to the heat wave. “The doctor almost never indicates that a person died of heat, especially if it is an elderly person”, explain it demographer. “When an elderly person with several pathologies dies, during a heat episode for example, we do not know if it is the heat or one of his pathologies which is responsible”he continues.
In its calculation of excess mortality, INSEE takes the year 2019 as a reference, because it is the last reference year before the Covid-19 pandemic. INSEE has chooses not to select an older year, because “the further away we go, the more the increase in deaths is mechanical, due to the fact that the population is aging”, explains Sylvie Le Minez, head of the demographic and social studies unit at INSEE. If INSEE had selected another reference base, the result of the excess mortality calculation would have been different, upwards or downwards.
On his side, Santé publique France publishes an annual report for the summer which reports on the excess mortality attributable to heat waves, using another method. The number of deaths linked to heat waves is calculated by comparing the deaths of a given year with the mortality observed over a previous reference period, excluding disruptive elements. For the summer of 2019, a year marked by two episodes of heat waves, the results of Public Health France reported 1,462 deaths attributable to heat waves. Results for summer 2022 are to be released this fall.