Will global warming make us age faster? We know that heat waves can have very serious consequences on health, for example causing the death of more than 3,700 people in France during thesummer 2024, which come in addition to 5,000 deaths in 2023 and nearly 33,000 between 2014 and 2022This potentially lethal impact of extreme heat is explained in particular by the cardiovascular stress that these intense and continuous heat events cause. But in addition to these short-term consequences, heat could also harm health in the long term.
Researchers from the University of Southern California (USA) have shown, in an article published on February 26, 2025 in the journal Science Advances, that people who live in places more exposed to these extreme heats age more quickly, causing a more rapid deterioration of their health.
Disadvantaged populations are more exposed to extreme heat
The study authors examined the impact of heat on nearly 4,000 men and women from across the United States. Each had a blood test to determine their biological ageThe scientists then analyzed temperature variations in the participants' living spaces during the six years prior to the blood test.
In the year prior to taking the drug, participants experienced an average of 127 days of intense heat, including six days of extreme heat. These periods of intense heat were particularly prevalent among people with low incomes, those with low education levels, African Americans, and Latinos.
The more we are exposed to heat, the faster we age.
The discrepancy between chronological age and biological age, determined by analyzing the methylation DNA, was greater in participants who were most exposed to extreme heat. That is, the more days of extreme heat they experienced, the more their bodies aged prematurely. And this correlation remained true even when controlling for other socioeconomic or ethnic factors. In short, no matter the person, they will age faster if they are exposed to more days of extreme heat.
“ Participants who live in places where half of the days of the year are considered very hot (with a temperature above 32°C), such as in Phoenix, Arizona, were up to 14 months older biologically compared to those living in places with fewer than 10 very hot days per year.", specifies in a press release Jennifer Ailshire, study director and professor of gerontology at the University of Southern California.
Heat matters, but so does humidity
The authors caution that heat isn't the only variable to consider, as humidity can make things worse. Sweating, which cools the skin, is less effective in high humidity. Heat escapes through sweating thanks to the evaporation of sweat droplets. But if the air is too humid, these droplets will have more difficulty evaporating, and therefore less heat will be released. This combination of heat and humidity is particularly important to consider in older people, because they no longer sweat as well as younger people and therefore lose some of their ability to cool their bodies through the evaporation of sweat., adds Jennifer Ailshire.
The authors warn that the impact of heat on biological aging could become increasingly dangerous due to global warming, which is causing an increase in the number of very hot days per year. This is particularly true because this rise in temperatures is accompanied by an aging population. These people are more vulnerable, so we will have to think more about strategies to mitigate these high temperatures.", she warns. One more reason to take the fight against climate change seriously, as if there were any missing.
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