Living in extreme heat can age your body just like smoking does

Phoenix summers no longer just feel unbearable. They may age your body faster too. In 2023 alone, the city recorded over 140 days with temperatures surpassing 100°F.

Now, new research suggests that these extreme heat conditions do more than cause short-term harm.

A recent study published in the journal Science Advances has revealed that long-term exposure to high heat can speed up biological aging.

The researchers found that people in places like Phoenix show signs of accelerated aging at the molecular level.

Heat ages you like smoking

“The impact is similar to the effect of smoking and drinking,” said Eunyoung Choi, lead author and gerontologist at the University of Southern California.

Choi’s team compared older adults from across the U.S., including heat-struck Phoenix and cooler cities like Seattle.

People living in hotter areas appeared around 14 months older biologically than their cooler-region counterparts. These results reflect how consistent heat exposure may silently wear down the body’s internal systems.

Aging affects health and work

Boston University gerontologist Deborah Carr noted that even small differences in aging matter. “It’s just a tremendous strain not only on their own lives and the lives of their families and caregivers, but also has a larger societal impact.”

Faster aging may lead to earlier onset of conditions like diabetes, dementia, and cardiovascular disease.

If those health issues appear sooner, they may push people out of the workforce or into expensive, long-term care. “It really can have tremendous impacts,” said Carr.

Heat changes how your genes work

The researchers focused on biological age, not just chronological age. They used DNA samples to track changes linked to a process called methylation. This chemical process affects how genes behave. It acts like switches that can turn genes on or off.

Methylation doesn’t alter the DNA sequence but changes how genes are expressed. These shifts can occur in response to environmental stress, poor diet, inactivity, pollution, and heat.

The team used several epigenetic clocks to measure aging. These clocks rely on different sets of DNA methylation markers and offer insight into both pace and risk of biological decline.

Heat makes aging speed up

Increased heat exposure was linked to faster aging in several clocks. Short-term exposure, such as a few days or weeks, raised PCPhenoAge, a measure tied to general physiological aging.

Longer-term exposure, such as one to six years, also accelerated PCGrimAge and DunedinPACE, which reflect mortality risk and pace of decline.

Animal studies support this. Heat stress can leave a lasting “epigenetic memory” that alters how immune cells and heart cells function. These changes persist long after the initial heat exposure.

In humans, heat has been linked with reduced methylation of genes like TLR-2. This gene affects inflammation and immunity. Such changes may explain how heat accelerates disease onset.

Rising heat makes things worse

Emergency visits and deaths spike during heat waves. With climate change, those risks only grow. The U.S. may see 20 to 30 more extreme heat days each year by mid-century, according to the National Climate Assessment.

Choi warned that this rising heat comes as the population ages. Older people cannot cool themselves as efficiently. Medications and declining circulation increase their vulnerability.

But heat affects everyone. “It’s basically like if you’re trying to tread water and someone hands you a brick,” said Robert Meade, a heat physiology expert from Harvard. “It’s just an extra weight.”

Heat levels at home matter

What matters isn’t just the outdoor temperature. Conditions inside homes vary widely. Some people live in overheated trailers or apartments without cooling. Others have access to reliable air conditioning.

Future research aims to explore these differences. Personalized data could reveal how daily exposure shapes long-term health. That could guide public health policies.

Long heat exposure and aging

The researchers note that not all gene changes are harmful. Some may reflect adaptation that helps bodies handle heat better. But current evidence leans toward damage, not resilience.

Prolonged exposure may reduce physical activity, disturb sleep, and increase stress. These effects accumulate over time, pushing bodies into faster aging even without visible symptoms.

By capturing these changes with precision tools like epigenetic clocks, scientists now offer a clearer view into how heat transforms health at its core.

The study is published in the journal Science Advances.

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