2023-06-23 12:28:39
Since 2014, between June 1 and September 15, high temperatures have been responsible for nearly 33,000 deaths, calculates Public Health France.
This is a reality that France discovered in 2003, but which still surprises it every year in the heart of summer: even in our temperate country, the heat kills, and not only very old and fragile people. Since 2014, between June 1 and September 15, high temperatures have been responsible for nearly 33,000 deaths, according to Public Health France (SPF) which publishes this Friday an estimate of the weight of heat in mortality. That is an average of 3,600 deaths each summer, as much as the annual road mortality… “This impact corresponds to a small number of days per year, but can represent up to 9% of summer mortality (…), write the experts. By way of comparison, particulate air pollution is responsible for 40,000 deaths per year in France, i.e. approximately 7% of mortality, for exposure concerning the entire population on all days of the year.
Experts point out that it is impossible to directly and in real time count heat-related mortality, which has very varied effects on organisms, which participate in the decompensation of pre-existing pathologies, but also enter into synergy with d other phenomena such as air pollution. To obtain these figures, the epidemiologists therefore crossed the data obtained at the departmental level, on the one hand on the number of deaths recorded by INSEE, on the other hand on the average daily temperatures by distinguishing the days hotter than normal. , scorching days (defined by exceeding departmental alert thresholds for daytime and nighttime temperatures, for at least 3 days). They deduce an excess of mortality and calculate the weight of heat in it.
Their modeling is consistent with other estimates, they specify, but the calculation carried out at the departmental level may lack, on the one hand statistical power in certain sparsely populated departments which therefore count few daily deaths, on the other hand finesse in those which may present “significant variations in infra-departmental temperatures (…), in particular for the coastal or mountain departments” and where the urban density is heterogeneous.
Likewise, the impact of the Covid-19 pandemic is difficult to assess (it was able to “reduce the number of people very vulnerable to heat before the summer”, soberly notes the report to mean that some of the most fragile may have died from Covid before being exposed to heat, and conversely in others the temperature-related risk may have been aggravated by the disease).
7,000 dead in the summer of 2022
The impact of the heat varies of course from one year to another (1000 to 7000 deaths depending on the year) depending on the weather. Thus, SPF calculates that in the summer of 2021, with an average temperature of 19.9°C and only 9 departments having experienced a heat wave lasting an average of 7 days, the heat killed 1,927 people; while 2022, an exceptional year with its average temperature of 22°C and 69 departments having experienced a heat wave of 14 days on average (but up to 34 in Isère), saw nearly 7,000 people die of heat. The risk of death increases non-linearly with rising temperatures: all ages combined, it is 1.07 times higher at 24.2°C average daily temperature than at 19.8°C, but 1.25 times more at 28.5°C. Moreover, if the risk of death is highest within 24 hours of exposure to heat, it can last up to 10 days afterwards.
The impact is “not limited to the most extreme periods”, and hot days are responsible for more deaths in total than scorching days.
A third of deaths occur during heat waves, which between 2014 and 2022 represented 6% of the days covered by the monitoring system set up each year from early June to mid-September. But the impact is “not limited to the most extreme periods”, insists SPF, and “simply” hot days, less dangerous but more numerous, are in total associated with more deaths than scorching days. “The organization of a specific response during heat waves is necessary, given their potential for massive and rapid disorganization of the healthcare system, as was observed in 2003”, therefore agree the experts. But it must be complemented by “structural and systemic adaptation to heat to reduce the risk to human health throughout the summer.”
Global warming
Especially since things are not going to get any better, with global warming promising us hotter summers and extreme climatic events (heat waves, droughts and associated fires). “The very significant impact observed in 2022 compared to other years foreshadows the challenges to come, therefore underlines SPF: very high temperatures all summer long, with extreme peaks, and a risk aggravated by a pandemic (of Covid-19 , Editor’s note) and probably by the air pollution generated by the fires locally. “Heat is one of the most worrying risks in Europe,” said Sébastien Denys, Environmental and Occupational Health Director at SPF, at a press conference.
People who died from the heat are often perceived as very fragile people whose death would have been brought forward by only a few days. However, there is no proof of this “harvest effect”.
They also emphasize that the deaths observed do not only concern very old and/or very fragile people. A third of the deaths counted by SPF concern people under the age of 75, and the deceased were not all at the very end of their lives. “People who died from the heat are often perceived as very fragile people whose death would have been brought forward by only a few days. However, there is no proof of this “harvest effect”. Thus, studies have calculated that during the heat wave of 2003 in France, “only a third of the deaths observed (…) would have been advanced by less than a year”, recalls the report. In addition to its now classic messages broadcast to the most vulnerable people, Public Health France will now address two new audiences, occupants of housing exposed to heat and athletes, “who are vulnerable to heat but do not do not identify it as such,” says Sandrine Randriamampianina, Head of Unit in the Department of Prevention and Health Promotion at SPF.
The burden on the healthcare system
And all of this has significant consequences for the healthcare system, which is already very fragile. Each year since 2019, more than 10,000 emergency visits, sometimes up to 20,000, and very many consultations in town, are justified by heat-related symptoms. In addition to the symptoms directly related to heat (hyperthermia, dehydration, hyponatremia – decrease in the concentration of sodium in the blood – …), being exposed to it increases the risk of cardiac, respiratory, cerebrovascular, renal decompensation, diabetes or psychiatric illnesses. It also modifies the activity in the body of certain drugs, and impacts the health of pregnant women and toddlers. “The number of heat-related deaths, therefore conclude the experts, therefore only represents part of the total impact on health in terms of morbidity and mortality”.
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