Spending a lot of time in the heat this summer? Your body might age faster

South China Morning Post

6 days ago

There's no doubt about it: It's getting hotter out there. Now, according to a new study, scientists have discovered that extreme heat may affect how we age.
For older adults, it means the summertime may come with some unexpected challenges.
It's getting hot, hot, hot
Last year was the hottest on record for the entire planet, topping 2023's already record-setting average temperature.
This season isn't looking much better.
The first months of 2025 have already included some record breakers, according to the National Oceanic and Atmospheric Administration's National Centers for Environmental Information.
Western Europe sweltered through hottest June on record
How heat can age you
Published in Science Advances, a 2025 study from the University of Southern California discovered that being exposed to a heat index over 90 degrees Fahrenheit (32 degrees Celsius) can accelerate biological aging. Heat index is what the temperature feels like when air temperature is combined with relative humidity.
Study participants who lived in places where heat days – defined as days with a heat index of 90 degrees or hotter – occur half the year 'experienced up to 14 months of additional biological aging compared to those living in areas with fewer than 10 heat days per year,' co-author Eunyoung Choi said in a news release.
While chronological age measures the number of years a person has been alive, biological age refers to how a person's body is aging – which can be measured by many different factors, according to the Mayo Clinic in the US.
'Even after controlling for several factors, we found this association,' Choi said. 'Just because you live in an area with more heat days, you're aging faster biologically.'
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Higher biological aging is associated with higher risks of disease and mortality. In the study, some older adults were biologically aged by extreme heat within seven days of exposure.
'It's really about the combination of heat and humidity, particularly for older adults, because older adults don't sweat the same way,' senior study author Jennifer Ailshire said in a news release. 'We start to lose our ability to have the skin-cooling effect that comes from that evaporation of sweat. If you're in a high humidity place, you don't get as much of that cooling effect. You have to look at your area's temperature and your humidity to really understand what your risk might be.'
According to Ailshire, the results show it's time to start finding better ways to cool off global warming. If we don't, older adults may suffer from the heat the most.
'If everywhere is getting warmer and the population is aging, and these people are vulnerable, then we need to get really a lot smarter about these mitigation strategies,' she said.