How Extreme Heat Can Speed Up Aging

Plus, what you can do to keep cool when temps start to climb

Kristen Fischer,

AARP

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En español

Published May 22, 2025

JAMIE CHUNG/TRUNK ARCHIVE

Extreme heat can do more than make you sweat. According to a new study, it can make you age faster too.

The study, published recently in the journal Science Advances, shows that ongoing exposure to heat over 80 degrees accelerates biological aging, which is how your body ages on the inside at the cellular level, regardless of how many birthdays you’ve had.

This might mean, for example, that instead of getting a specific health condition at a certain older age, it happens earlier, says Deborah Carr, director of the Center of Innovation in Social Science at Boston University, who studies heat and aging.

“[It] means you [have] more years of suffering, more years of demands on your caregiver,” Carr explains. It also means you may not have Medicare in place to properly care for any premature health problems that arise, she notes.

Heat’s impact on the aging process

If you’re living in an area with extreme heat for half the year, you could be even more prone to faster aging, the study found. In fact, for people living in hot climates, biological aging sped up nearly three years in some cases.

For the study, a team of researchers at the Leonard Davis School of Gerontology at the University of Southern California used different biological clock models to measure markers of aging in blood samples from 3,686 American adults, ages 56 and older. The researchers then compared each individual’s aging outcomes, measured by slight changes in their DNA, with their geographical heat index, considering heat and humidity.

Researchers categorized hot days as those that were 80 to 90 degrees, 90 to 103 degrees, and 103 to 124 degrees. They found that people who lived in areas that experienced more days of extreme heat were more likely to see greater increases in their biological age compared with people who experienced fewer hot days.

“Participants living in areas where heat days, as defined as Extreme Caution or higher levels [90 degrees and up], 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,” study coauthor Eunyoung Choi said in a statement. “Even after controlling for several factors, we found this association. Just because you live in an area with more heat days, you’re aging faster biologically.”

How heat affects your health

Biological age varies for everyone because it’s based on how your cells age. Chronological age, meanwhile, refers to how long you’ve been alive. One of the ways scientists measure biological age is based on methylation — a process that changes DNA.

“When you have extreme heat or when you’re exposed to it, it causes stress to your body. That stress can manifest, particularly in your cells, by changes in your DNA,” explains Arnab Ghosh, M.D., an assistant professor of medicine at Weill Cornell Medicine who studies the effects of extreme heat on older adults.

It’s not just heat that can affect a person’s biological age, Ghosh says. Lifestyle choices, such as smoking or having a condition like diabetes, can change it too.

Some evidence suggests that accelerated biological aging could raise the risk of dementia; it has been linked with other health issues, too, including diabetes, cardiovascular disease and respiratory disease. Heat can also raise the risk of heart attack and stroke, according to research.

Ghosh notes that heat can be harder on some older individuals, including people who take certain medications or have other chronic conditions. Women may also be more susceptible to complications from heat, according to a study published in 2024, which found that women ages 40 to 64 were as vulnerable to the effects of heat as men ages 65-plus.

“Whether that [heat-related stress] leads [directly] to problems or aging or advanced aging is still an open question,” Ghosh says. And researchers aren’t sure if heat stress effects are permanent, he adds.

Your personal heat baseline

Being in 90-plus-degree weather isn’t a standard cutoff for when heat stress begins. Everyone has a different threshold, meaning you can still experience heat stress at 80 degrees, for example.

People who live in warmer climates year-round may partly adapt to the heat naturally, but it can be harder during a heat wave. If you live in Arizona, for example, you may have a different baseline than someone who lives in Montana — a phenomenon known as acclimatization, Ghosh says.

Everything from your behavior and age to chronic conditions and what you wear can influence your risk for heat stress, Ghosh says, and scientists don’t know the threshold for each person.

A 2021 study showed that being in 75.2 degrees continuously without proper cooling can affect your body. “That can really have a significant wear and tear on the body, especially at night,” says Carr.

A certain temperature can feel different in various places — it may be cooler near a beach but feel warmer in a city with little breeze, Carr says. Knowing your threshold can get complicated if you spend part of your year in a hotter area and the rest in a cooler climate, she adds.

Plus, structures in areas that are warmer year-round likely have air conditioning, but that’s not the case in cooler areas, especially where older homes are common, Carr points out.

5 ways to ward off heat’s harmful health effects

You can’t stop the temps from climbing, but there are a few ways to stay safe in the heat — and perhaps ease the heat stress that could make you age faster.

1. Stay alert. Watch the news or stay up to date on advisory warnings so you can adapt what you do, how you hydrate or what you wear, Ghosh says. “As temperatures warm up, people have to be more aware of the environment around them and adjust accordingly,” Ghosh adds. The first heat wave of the season can be the worst on health, he says.

2. Avoid extreme temps. The hottest time of the day is during midday hours— a good time to stay indoors in air conditioning, especially during a heat wave, Ghosh says. If you know you don’t do well in high heat, don’t run errands at the hottest times of the day. As you get older, you may not be able to do things at midday that you could do just a few years ago, Carr explains. “People really need to be mindful about altering their behaviors [when it’s hot],” Carr adds.

3. Watch your meds. Certain medications, such as those for high blood pressure or heart disease, may raise your risk for fainting in high heat. Know if any drugs or supplements you take could make you less tolerant to the heat, Ghosh says. Keep your medications out of the heat too, Carr adds, since exposure to varying temperatures can alter them chemically.

4. Keep cool at night. Sleep in a lower temperature to avoid heat stress — especially if you already have trouble sleeping, Carr says.

5. Plan for the heat. “Have a climate plan just the way you might have a will,” Carr advises. Know where you can go if you need to leave your home or what to do if you don’t have power due to high heat. “That can be really helpful, especially for older people,” Carr says.

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Kristen Fischer is a contributing writer at AARP based at the Jersey Shore. She has also written for Health, WebMD, and McKnights and is the author of Zoo Zen: A Yoga Story for Kids.