A new study published in the journal Science Advances revealed findings on the impact of extreme heat exposure on biological aging in older adults. The study was conducted by researchers Eunyoung Choi and Professor Jennifer Ailshire from the University of Southern California.
The researchers analyzed data from nearly 3,700 participants aged 56 and older across the US, with an average age of 68 years. They used epigenetic clocks to analyze methylation patterns in the blood samples of older participants at different time points, providing an estimate of their biological age, according to The Sun. Biological aging is a measure of the body's ability to function at the molecular, cellular, and functional levels, differing from chronological age, which is based solely on the date of birth.
The findings showed a correlation between long-term heat exposure and biological aging in older adults, with short and mid-term heat increasing biological age by 1.07 years and longer-term heat exposure increasing it by up to 2.48 years, according to ABC News. "It's really about the combination of heat and humidity, particularly for older adults, because older adults don't sweat the same way," said Professor Ailshire.
Ailshire explained that residents of Phoenix, Arizona, where half of the year has Extreme Caution level heatwaves, experienced up to 14 months of additional biological aging compared to those in areas with fewer than 10 heat days a year. In their study, Choi and Ailshire first determined the biological age of the participants and examined whether they had experienced extreme heat at their residence in the six years prior to blood sampling, according to The New York Times.
The findings came as the climate crisis made extreme heat more frequent and intense across the world, raising concerns about its impact on public health and molecular aging. "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," concluded Ailshire, according to The Independent.
Ailshire said that city planners and policymakers might consider ways to reduce the impact of heat on seniors, such as providing more shade, planting more trees, and increasing urban green space. The authors emphasized that there is not enough data to definitively conclude that heat exposure caused the acceleration in aging—only that the two appear linked.
Researchers plan to investigate other factors that might make some people more vulnerable to heat-related biological aging and how this aging might affect a person's overall health. Rachel Morello-Frosch, an environmental health scientist at the University of California, Berkeley, said there is some debate among scientists about whether epigenetic clocks are the best measure for aging. "How to best measure biomarkers, and how to use them to predict future health, is an evolving space in the scientific field," stated Dr. Morello-Frosch, according to The New York Times.
The correlation remained even when other factors such as income, ethnicity, and lifestyle were taken into account. The study authors stated that the impact of extreme heat on the body is comparable to the effects of smoking, emphasizing the need to consider excessive heat as a serious environmental factor that shortens life.
Previous studies conducted in Germany and Taiwan had suggested that high temperatures can accelerate epigenetic aging markers, and the new research confirmed these findings in a representative sample of older adults from across the US. The connection between heat days and accelerated aging was evident even after relatively short periods—after seven days or one to two months—demonstrating that heat-induced epigenetic changes may accumulate over time.
Older adults are particularly vulnerable to extreme heat because their bodies struggle to regulate temperature efficiently. Extreme heat has been linked to negative health outcomes, including heart disease, increased mortality, and an elevated risk of aging-related diseases such as heart failure, diabetes, and stroke.
The article was written with the assistance of a news analysis system.