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Extreme heat is doing more than just causing discomfort during summer. A new long-term study has found that repeated exposure to heatwaves can accelerate biological ageing, with effects similar to those of smoking or a poor diet. Researchers warn that the cumulative impact of heat could leave people physically older than their actual age, raising concerns for populations already vulnerable to rising global temperatures.
Biological Ageing and Heatwave Exposure
The research, carried out over 15 years in Taiwan, tracked nearly 25,000 adults between 2008 and 2022. It measured biological ageing through health indicators such as blood pressure, cholesterol, kidney and liver function. Scientists discovered that every extra day of heatwave exposure translated into an average increase of about nine days in biological age. For those in physically demanding outdoor jobs, the impact was even more severe, equivalent to around 33 extra days of ageing per heatwave day.
This effect may appear small on a daily scale, but experts caution that when accumulated over years, it becomes significant. The findings suggest that prolonged heat stress quietly accelerates the ageing process, contributing to higher risks of chronic illnesses and other age-related health challenges.
Who Is Most Affected?
The study found that the ageing effects of heatwaves were most pronounced among groups already facing health or socioeconomic disadvantages. Elderly people, manual workers, and individuals from lower-income communities were particularly at risk, in part due to limited access to cooling measures such as air conditioning. Rural residents, who often face higher exposure to outdoor conditions, were also more affected than those in urban settings.
Interestingly, the research noted signs of adaptation over time. Communities with increasing access to cooling technologies or changing work practices appeared to experience a gradual reduction in the impact of extreme heat on ageing. However, unequal access to such protections means the benefits are not shared evenly across populations.
A Global Health Concern
The Taiwanese findings align with similar studies conducted in the United States, which have shown that older adults living in hot regions experience measurable biological aging, as detected through epigenetic changes. In some cases, this translated to more than a year of additional ageing over just a few years of exposure. Together, these studies highlight extreme heat as an invisible but growing health threat.
Prof Paul Beggs, an environmental health expert at Macquarie University in Sydney, said, “Many of us think we come through heatwaves without lasting harm, but this research shows they influence how fast we age.” He added, “In 2024, scientists found that early-life heat exposure can impair brain white matter development in children. Combined with this new evidence of accelerated ageing in adults, it signals a major shift in our understanding of heat’s impact on human health. The effects can occur at any stage of life and may be long-lasting.”
As heatwaves become more frequent and intense due to climate change, scientists say their impact is not limited to immediate dangers such as heatstroke. Instead, they contribute to a slow but steady erosion of health, shaping the long-term well-being of millions. The research highlights the need for strategies that protect outdoor workers, expand access to cooling systems, and reduce overall exposure, particularly in communities that are least able to adapt on their own.
References:
https://www.nature.com/articles/s41558-025-02407-w
https://www.nature.com/articles/s41558-024-02027-w
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Photo by Jose Antonio Gallego Vázquez on Unsplash
