Long-term exposure to extreme heat events accelerates the body’s ageing process and increases vulnerabilities to heath issues, finds a long-term study of 24,922 people in Taiwan.
The study, published today in Nature Climate Change, suggests that moderate increases in cumulative heatwave exposure increase a person’s biological age — to an extent comparable to regular smoking or alcohol consumption. The more extreme-heat events that people were exposed to, the more their organs aged. This is the latest study to show that extreme heat can have invisible effects on the human body and accelerate the biological clock.
Exposure to extreme heat, especially over long periods of time, strains organs and can be lethal, but “the fact that heatwaves age us is surprising”, says Paul Beggs, an environmental-health scientist at Macquarie University in Sydney, Australia, who was not involved in the research. “This study is a wake-up call that we are all vulnerable to the adverse impacts of climate change on our health. It reinforces calls for urgent and deep reduction in greenhouse-gas emissions,” he adds.
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Accelerating ageing
Age isn’t just a result of time. Previous studies have linked a number of factors — including environmental and social stress, genetics and medical interventions — to signs of ageing-related physiological changes. This puts people at a higher risk of cardiovascular disease, cancer, diabetes and dementia.
To study the long-term impacts of heatwaves on ageing, the researchers analysed data from medical examinations between 2008 and 2022. During that time, Taiwan experienced around 30 heatwaves, which the study defined as a period of elevated temperature over several days. The researchers used results from several medical tests, including assessments of liver, lung and kidney function, blood pressure and inflammation, to calculate biological age. They then compared biological age with the total cumulative temperature that participants were probably exposed to on the basis of their address in the two years before their medical visit.
The study found that the more extreme-heat events that people experienced, the faster they aged — for every extra 1.3 °C a participant was exposed to, around 0.023–0.031 years, on average, was added to their biological clock.
“While the number itself may look small, over time and across populations, this effect can have meaningful public-health implications,” says Cui Guo, an environmental epidemiologist at the University of Hong Kong, who led the study.
Manual workers and people living in rural areas experienced the largest health impacts, probably because these groups are less likely to have access to air conditioning. But there was an unexpected upside: the impact of heatwaves on ageing decreased over the 15-year study period. The reasons behind this heat adaptation are unclear, but improved access to cooling technology could play a part, Guo says.
Still, “the message is that heat makes you age a bit faster than you normally would, and that this is something you would like to avoid”, says Alexandra Schneider, an environmental epidemiologist at Helmholtz Munich in Germany, who was not involved in the study.
Rising heat
In 2023, research in Germany found that higher air temperatures were associated with more epigenetic markers of ageing. And a study in more than 3,600 older people in the United States similarly concluded, through analysing DNA markers, that extreme heat prematurely aged participants.
The most recent study focused on the impact of long-term heat exposure, which is more likely to have lifelong health effects. This is important because climate change is leading to more extreme-heat events. In the United States, there are now six heatwaves each year, as of 2010 — up from two in the 1960s. Scientists estimate that climate change has made heatwaves such as the deadly 2022 ones in Pakistan and India, during which temperatures hit 50 °C, 30 times more likely to occur.
The growing frequency of heatwaves, combined with their effects on health, highlights the importance of protecting vulnerable groups, says Guo. “Heatwave is not a personal risk factor, but a global concern.”
This article is reproduced with permission and was first published on August 26, 2025.