2023-08-23 12:39:23
DECRYPTION – The southern half of France has been affected for several days by a record heat wave which puts the body to the test. However, not everyone has the same tools to adapt.
The heat wave that has been hitting the southern part of France for the past few days has affected nearly 30 million French people. And some more than others. “I can’t sleep at night, I can’t take it anymore“, blows Christophe, a neo-Bordeaux in his sixties. “I’ve been living in the Southwest for two years and I can’t get used to it».
The just retired explains that he cannot bear these heats. Unlike his son who is doing like a charm, except for the extremely rare days at over 40°C. How to explain that organisms react so differently?
Extreme ages
«We are homeostatic beings“Says Dr. Richard Handschuh, member of the MG France union, from the outset. In concrete terms, humans must maintain a constant temperature, around 37° C. When the outside temperature rises, the body must evacuate excess heat to avoid overheating. Our organization has for thisa central internal temperature control system“, specifies Bruno Megarbane, head of the medical and toxicological resuscitation department at the Lariboisière hospital, in Paris. This is the role of sweating by evaporation or vasodilation of the vessels. “These phenomena can malfunction in certain individuals and this translates into a certain predisposition to make heatstroke in the event of a heat wave“, explains Doctor Megarbane.
The extreme ages, that is to say infants or the elderly, correspond to periods of life when the body has difficulty adapting to high temperatures, says the head of department. How to explain it? “The elderly feel very little heat and therefore sweat little, which raises the overall temperature of their body“, details Dr. Richard Handschuh. The latter are thus more victims of hyperthermia. “Infants, on the other hand, only expel heat through the face.“continues the member of the union of general practitioners. Their body temperature rises much faster.
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Genetic factors and habits
Another source of inequality comes this time from genetic factors. “Populations that have lived in warm areas for a long time are certainly more resistant“, as in the tropics, says Dr. Megarbane. This heat resistance is the product of a very long time as it has developed over several generations. “Those who survived the’time when there was not yet medicine as we know it had natural abilities that allowed them to be better adapted to the environments in which they found themselvesexplains Dr. Handschuh.
However, this genetic dimension is not insurmountable. Being regularly exposed to heat can also play a role. “The body develops a greater capacity to supportif it is regularly exposed to high temperatures, explains Richard Handschuh. The human body can thus, over a shorter time, adapt physiologically. It can be observed “an increase in sweating capacity, activation of hormones that adapt water and sun retention in relation to losses or even cardiovascular performance», Details Dr. Bruno Megarbane.
Illnesses and medication
A final vulnerability factor concerns the medical condition of individuals. “People with comorbidities or even chronic illnesses are more vulnerable because their adaptive physiological system is less able to make the changes necessary for their body to lose heat.», Details Dr. Bruno Megarbane. Ditto for people who use drugs or alcohol.
Taking certain medications can also penalize certain organisms in the face of high heat. “Certain medications block sweating such as neuroleptics, antidepressants, antiparkinsonianssays Dr. Megarbane. And they are not alone. Medicines for heart patients, which slow down the heart, or even diuretics endanger the organisms in the event of high heat because they modify the adaptation to hyperthermia.
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Drugs that slow the heart can “decrease the mechanism that allows perspiration and dilation of vessels in the skin and perspirationexplains Richard Handschuh. Because to evacuate the heat,the body increases the heart rate to vasodilate the vessels». Diuretics, on the other hand, have dehydrating effects on the body. “People on diuretics may find themselves dehydrated as they pass more fluid through the urine.“, he assures. In hot weather, it can therefore be “advised» the persons concerned to reduce the intake of these drugs, under the supervision of a doctor.
For scientists,lifestyle adaptation» thus becomes the watchword to follow. Concretely, it is a question of avoiding physical activities in full sun, of preventing as far as possible the isolation of the most vulnerable, of building more ventilated housing or even, if possible, of equipping oneself with a air conditioner. “In the early 2000s, people n’did not have all these practices in mind“recalls Dr. Megarbane. Before adding:Since then, we have significantly strengthened individual defenses against heatstroke.“. More generally, in the face of this type of temperature, everyone is invited to be cautious.
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