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A new study published in Science Advances suggests that prolonged exposure to extreme heat can accelerate biological ageing, making people effectively older at a cellular level. Researchers at the University of Southern California (USC) analysed blood samples from nearly 3,700 older adults and found that those living in hotter regions of the US aged faster biologically. They used an epigenetic clock—a tool that measures DNA changes over time—to assess biological age and compared the results with local heat index data. Their findings revealed that exposure to extreme heat, particularly temperatures above 32.2°C, could increase biological age by up to 2.48 years, an effect comparable to smoking.
Jennifer Ailshire, senior author of the study and professor of gerontology and sociology at USC, explained that older adults are particularly vulnerable to heat stress because their bodies regulate temperature less efficiently. High heat and humidity reduce the body’s ability to cool itself, which may lead to inflammation and cellular damage, accelerating the ageing process. The study found that individuals living in extremely hot areas, such as Phoenix, Arizona, experienced up to 14 months of additional biological ageing compared to those in cooler regions.
With climate change driving more frequent and intense heatwaves, the study highlights the growing public health threat posed by extreme heat. Older adults face increased risks of age-related diseases such as heart disease and cognitive decline. Ailshire emphasized the need for better urban planning and mitigation strategies, such as expanding green spaces, improving shaded areas, and ensuring access to cooling centres, to protect vulnerable populations from long-term heat exposure.
