Extreme heat may be silently speeding up biological aging in older adults, a new study from the University of Southern California’s Leonard Davis School of Gerontology has warned. 

The study, led by gerontology experts Eunyoung Choi and Jennifer Ailshire, analyzed data from over 3,600 U.S. adults aged 56 and older. The research team used advanced DNA-based aging markers, and found a clear link between heat exposure and accelerated aging. Participants in regions like Phoenix, Arizona, where heat days (above 90°F on the heat index) occur for half the year, showed significantly faster biological aging compared to those in cooler areas with fewer than 10 such days annually.

“We’re seeing that heat can age you biologically in ways similar to smoking or heavy drinking,” said Choi, a USC PhD alumna and co-author of the study. “For older adults, who are already vulnerable, this is a serious wake-up call.”

Choi continued: “Participants living in areas where heat days, as defined as Extreme Caution or higher levels (≥90°F), occur half the year, such as Phoenix, Arizona, experienced up to 14 months of additional biological aging compared to those living in areas with fewer than 10 heat days per year.” 

Even short bursts of heat accelerate age

The researchers used the National Weather Service’s heat index, which combines temperature and humidity to reflect how heat feels to the human body. They tracked effects over various time frames—ranging from a single day to six years—and found aging acceleration even in short bursts of heat. For example, a single day of “caution-level” heat (80°–90°F) was linked to over a year of additional aging, while six years of frequent “extreme caution” heat (90°–103°F) boosted aging markers by up to 5%.

Jennifer Ailshire pointed to the unique risks for older adults. “As we age, our bodies don’t cool off as efficiently through sweating, especially in humid conditions,” she explained. “That makes heat a bigger threat—and with climate change making summers hotter, we need smarter ways to protect people.”

India’s scorching summers and record-breaking heatwaves in the US underline the growing threat of extreme weather. The implications of the study,  published in Science Advances, extend beyond biology, hinting at increased risks for age-related conditions like heart disease and kidney problems, which are already tied to heat stress.

Ailshire called for action, urging cities to invest in green spaces, shade structures, and other cooling measures. “If the planet keeps warming and our population keeps aging, we can’t ignore this,” she said. 

The researchers plan to dig deeper, exploring how specific DNA changes tie into heat and whether these effects hit certain groups harder.

Also read: Sunscreen, Vitamin D & Skin Cancer: Stay Safe in the Sun