Several scientific studies indicate that women – especially over the age of 65 – have a greater risk of dying during periods of heat wave. A gender inequality that is beginning to be taken seriously and the reasons for which are still poorly understood.
Hundreds people have already died because of the high temperatures which are suffocating Europe in this summer of 2022. Enough to fear the worst on the number of deaths caused by this heat wave. In France, that of 2003 – a period during which France recorded an excess of deaths of 15,000 people – prompted the authorities to multiply the warnings.
Unsurprisingly, awareness-raising efforts have primarily targeted the elderly and those with comorbidities, who are the most affected by heat waves. But it would seem that there is not only an age-related inequality in the face of high heat.
“The health risks are also greater for women than for men”, writes the British daily The Guardian. The hypothesis that the heat wave kills women more is relatively recent.
Health risks greater for older women
She had experienced a first illustration in France in 2003. “When we observe populations in different age groups, we see that during this heat wave the mortality rate among women was on average 15% higher than among men” , wrote Dutch researchers who, in an article published in 2018, analyzed around 60 studies between 2000 and 2016 focusing on mortality during heat waves.
Another study, still conducted in the Netherlands in 2021, refines this observation a little. Looking at the death rate linked to extreme temperatures in the country, scientists from the University of Amsterdam have found that the gap between the number of deaths among men and women during the hottest periods increases. with age, especially after age 65.
The scientific literature devoted to this phenomenon is not yet very dense, and “it is therefore still too early to draw definitive conclusions, but the data point very seriously to a correlation between sex and the risk of death during heat waves” , notes Simon Cork, physiology specialist at Anglia Ruskin University in the city of Cambridge.
The scientific corpus has, in any case, seemed sufficient to the British government who added women people over 75, young children, and people suffering from a serious illness or a significant psychiatric disorder on the list of citizens most at risk during the heat wave.
Less perspiration and longer life?
The British authorities do not indicate, however, why women are more likely to die of heat. No wonder: the reason for this gender inequality in the face of high temperatures still remains largely a mystery.
Scientists have no shortage of hypotheses. Starting with a long list of physiological factors that could play a role. “The simplest explanation is physical and relates to the fact that women’s bodies, which are generally smaller than men’s, heat up faster,” said Mike Tipton, a researcher at the University of Portsmouth who has studied the reactions of the body in extreme situations.
In this hypothesis, as the body heats up more quickly, the heart starts moving more quickly to react to the thermal shock, “which would increase the risk of cardiovascular accident”, summarizes this scientist.
Women also sweat less than men, “especially when they are older,” says Simon Cork. And yet, “it is practically the only natural cooling mechanism of the body, since it is the process of evaporation of body water which has warmed up under the effect of exertion or heat. “, explains this specialist.
To complete this picture, “we must not forget that the feeling of thirst diminishes with age, which means that the elderly may tend to forget to hydrate themselves”, adds Simon Cork. It is therefore a cocktail of physiological factors that would make it possible to better understand why women of advanced age are more at risk.
“We can add to this, the fact that they tend to live longer than their partner,” says Mike Tipton. They therefore find themselves more often alone at home, and “we know that isolation plays a role in mortality during heat waves” because single people make less effort to take care of themselves, underlines the scientist from the portsmouth university
A public toilet problem in Asia
But “I think that social and environmental factors play an equally important role in explaining this excess female mortality”, assures Ilan Kelman, specialist in health issues at University College London (UCL) who works on the health impact of natural disasters.
The differences in behavior between men and women, linked to social contexts, “has often played an important role in explaining the differences in mortality during natural disasters”, notes this specialist. He explains that one of the reasons why there are more men who die during fires is because they are the ones who often intervene on the front line (the job of firefighter being very masculine, for example) . During epidemics, it is often women who are the first to be affected in societies where they mainly occupy the jobs of caregivers and nurses.
Heat waves would not be so different from other natural disasters in this respect. “In Asia, for example, we noticed that there were more women who died during heat waves because, in particular, of a problem of access to public toilets”, underlines Ilan Kelman. Indeed, the hotter it is, the more you need to hydrate and the more you want to urinate. “For men, the absence of public toilets is less serious because it is more socially accepted that they relieve themselves in public, while this is not the case for women, some of whom will prefer not to drink for minimize the risk of having to find a toilet”, summarizes the UCL researcher.
This example may seem anecdotal, but it proves that the issue of gender inequality in the face of the heat wave “probably stems from a mixture of physiological, behavioral and social factors”, says Mike Tipton.
For him, “until we are fixed” on the reasons why heat waves are more deadly for women, “it will be impossible to provide an effective response”. We will not know, for example, if it is better to develop treatments to promote perspiration, to work on drugs that act better on the heart rate or if it is almost more effective to just visit your aging grandmother. to make sure she takes care of herself by hydrating.