New research is raising alarming concerns about the long-term health impact of climate change and extreme heat on older adults.
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A new study from the University of Southern California's Leonard Davis School of Gerontology suggests that exposure to higher temperatures could accelerate biological aging, particularly in those aged 56 and up -- potentially contributing to a greater risk of chronic diseases and early death.
The study, published in the journal Science Advances, examined more than 3,600 participants aged 56 and older. By analyzing blood samples and studying epigenetic changes over a six-year period, researchers were able to estimate participants' biological ages. Biological age refers to how well the body functions at the molecular level, which can differ from one's chronological age. Higher biological age is linked to a greater risk of mortality and disease.
The findings revealed that individuals in areas with more heat days — especially those exceeding 90°F — showed up to 14 months of additional biological aging compared to those in cooler regions. This effect persisted even after accounting for factors such as lifestyle choices, physical activity, and socioeconomic status.
"Just because you live in an area with more heat days, you're aging faster biologically," Jennifer Ailshire, senior author and professor of gerontology and sociology at the USC Leonard Davis School, said in a statement.
The research found that heat-induced changes could happen relatively quickly, with some lasting effects accumulating over several years.
The impact of extreme heat on biological ageing remains unclear, but it has been linked to negative health outcomes such as heart disease and increased mortality.
While high temperatures have long been linked to adverse health outcomes, this study is one of the first to show that the combination of heat and humidity — especially in older adults — can have a direct impact on biological aging.
Older adults have a reduced ability to sweat, which makes it harder for their bodies to cool down during hot, humid weather.
"It's really about the combination of heat and humidity, particularly for older adults, because older adults don't sweat the same way. We start to lose our ability to have the skin-cooling effect that comes from that evaporation of sweat," Ailshire explained. "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."
Researchers say these findings could have profound implications for public health as climate change intensifies, especially in cities where extreme heat events are becoming more frequent. The study calls for more heat mitigation strategies in urban planning, such as creating shaded areas and increasing green spaces, to protect aging populations.
"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," said Ailshire.
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