Repeated exposure to heatwaves is accelerating biological ageing in humans, according to a new study published in Nature Climate Change. The impact is comparable to the damage caused by smoking, poor diet, or lack of exercise, researchers say. As extreme temperatures become more frequent due to the climate crisis, billions of people could face long-term health consequences.
The study followed 25,000 adults in Taiwan over 15 years, comparing their exposure to heatwaves with their biological age—a measure of overall health based on medical tests. For example, experiencing four additional heatwave days over two years was linked to a biological age increase of about nine days. Manual workers, who spend more time outdoors, saw an increase of 33 days.
While the individual effect may seem small, the researchers warn that cumulative exposure over decades could be significant. “If heatwave exposure accumulates for several decades, the health impact will be much greater than we have reported,” said Dr. Cui Guo of the University of Hong Kong, the lead author. Heatwaves are also becoming longer and more frequent, exacerbating the risk.
The exact mechanism behind heat-induced ageing is unknown, but DNA damage is thought to play a role. The study accounted for factors like weight, smoking, and pre-existing conditions, but lacked data on time spent outdoors or air conditioning use. Experts say the findings represent a “paradigm shift” in understanding heat’s long-term health effects, which can occur at any age and be lifelong.
