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July 4, 2023 was the hottest day ever recorded on Earth, according to the US Oceanic and Atmospheric Observation Agency (NOAA). The average temperature reached 17.18°C. In a context of high temperatures linked to global warming, scientists have wondered what temperature are we able to withstand without endangering our health.
As we know, the increase in the average temperature of the Earth has devastating consequences on the planet: melting glaciers, disappearance of certain animal and plant species, increasingly violent natural disasters… But it would also have consequences on our health.
Health in danger from 40°C
A study presented at the SEB Centenary Conference in Edinburgh (Scotland), for the first time set a temperature limit beyond which the organism would be threatened. Professor Lewis Halsey and his team of researchers reveal that temperatures that fluctuate between 40 and 50°C are potentially dangerous for health. Their work is a continuation of a previous study published in 2021 in the journal Physiological Reports. This asserted that high temperatures cause an acceleration of the functioning of the metabolism. As a reminder, metabolism refers to all the chemical reactions that produce the energy necessary for the functioning of our body.
“From 40°C, metabolism increases by 35% compared to its normal rate, and by 48% when the body is exposed to a temperature of 50°C”, says Dr. Daniel Atkinson, a pain specialist, who did not participate in these two studies. “The hotter it is, the harder the body has to work to maintain vital functions“, he added.
Professor Halsey’s study also looked at how heat affects heart function and the differences between men and women. In particular, the researchers found that the increase in heart rate related to heat was more pronounced in women than in men.
We are not all equal when it comes to the effects of heat
The consequences of extreme temperatures on health vary from person to person. The most vulnerable people are the elderly, children, pregnant women, people suffering from a chronic illness and those who have limited access to the means to better withstand the heat (air conditioning, fan, water points, access to drinking water…).
During hot weather, we sweat more, are at greater risk of dehydration, dizziness, nausea, headaches, fatigue, muscle cramps and palpitations. In extreme cases, high temperatures can cause death, especially during heat waves. The cause is heat stroke, which causes a dangerous rise in body temperature that can lead to serious neurological symptoms and even death.