A new study found that living in areas in the U.S

Science Says Extremely Hot Weather Could Speed Up Biological Aging with extreme heat may speed up biological aging in older adults. Here's what to know

• A new study found that adults ages 56 and older who lived in areas with more heat waves had accelerated biological aging.
• Biological age refers to the age of your cells, not the amount of time that has passed since your birth.
• The research didn't prove causation—only that extreme heat was linked with higher biological age.

The climate where you live might influence how fast you age on the cellular level, according to a new study.

Compared to people living in cooler areas, those residing in regions with more frequent extreme heat had an accelerated biological age—the age of cells rather than how much time has passed since birth, researchers reported in Science Advances.

As climate change progresses, more people around the world are experiencing very hot temperatures. In the United States alone, the average heat wave season has been 46 days longer in 50 of the nation’s largest cities than it was in the 1960s. 

Heat waves can have devastating health consequences, especially for older adults. Sweltering conditions can increase the risk of hospitalizations, cardiovascular disease, kidney dysfunction, and mortality, study co-author Eunyoung Choi, PhD, a postdoctoral associate at the Leonard Davis School of Gerontology, University of Southern California, told Health. 

The new findings offer fresh insight into how these conditions might develop. “The effects of extreme heat might not show up right away as a diagnosable health condition, but they could be taking a silent toll on our body,” Choi said. “We aimed to uncover these hidden effects of heat on the body, an important precursor before they turn into more serious health outcomes.”

How Heat Affects Biological Aging

For their research, Choi and her colleagues relied on blood samples taken from 3,679 participants ages 56 or older enrolled in the national Health and Retirement Study. 

They examined the samples, collected at different points over six years, for epigenetic changes—a measure of how external environmental factors hit the “on” and “off” switch for individual genes by a process called DNA methylation. To quantify these changes, the team used epigenetic clocks, tools that estimate biological age based on methylation patterns.

“These clocks offer one of the best tools we currently have for assessing how environmental exposures affect biological aging,” Choi said.

The scientists then compared shifts in people’s biological age to the historical heat index readings of their location and the number of heat days recorded by the National Weather Service’s Heat Index Chart between 2010 and 2016. Phoenix and Tucson in southern Arizona, Brownsville and Laredo in southern Texas, and Florida’s Miami and Tampa emerged as some of the hottest regions.

“These locations experienced a high number of extreme heat days, defined as days when the heat index reached or exceeded 90°F,” Choi said. “Some of these regions recorded more than 140 extreme heat days per year, making them among the most heat-exposed areas in the country.”

Participants living in these areas experienced up to 14 months of additional biological aging compared to those residing in regions with fewer than 10 heat days per year. These links held up even when researchers considered factors such as physical activity, alcohol consumption, and socioeconomic differences.

“While a few previous studies have suggested heat exposure could influence aging, they were often limited to smaller, specific populations,” Choi said. “By leveraging a nationally representative sample of older U.S. adults, our study provides broader evidence that chronic heat exposure may accelerate biological aging at the population level.”

As for how this might happen, Choi pointed to higher temperatures potentially triggering cellular stress and inflammation, as well as influencing DNA methylation patterns. That can suppress or activate genes, potentially leading to systemic aging effects, Choi said.

Should You Worry?

These results might seem scary if you’re older and live in a hot climate, but keep in mind that the study shows only an association between accelerated biological aging and frequent bouts of extreme heat—it doesn’t prove causation.

The authors noted that the study also has some drawbacks. For example, researchers didn’t have information about a participant’s air conditioning use, which could have had a “mitigating” effect on residents. Plus, the “validity” of using epigenetic clocks across genetically and environmentally diverse populations hasn’t been established—and researchers don’t know if the epigenetic changes they saw are even that bad. They may represent “adaptive responses to heat” rather than “solely maladaptive changes associated with accelerated aging.”

Also, remember that the “findings don’t mean that every person living in hotter areas has an older biological age,” Choi added. “Rather, on average, people in hotter regions tend to show signs of faster aging. Two people living in the same neighborhood may have very different heat exposures based on lifestyle and socioeconomic factors.”

Future research, such as that focusing on more subtle temperature changes, is needed to have a fuller understanding of this pressing topic, said Barrak Alahmad, MD, MPH, PhD, an instructor in environmental health at the Harvard T.H. Chan School of Public Health. 

Staying Safe

Regardless of whether accelerated biological aging is at play, it’s clear that heat waves can be dangerous for aging populations. Experts didn’t mention going to extreme lengths like moving, but they did suggest taking extra precautions when temperatures rise.

To stay safe, Tarik Benmarhnia, PhD, an associate professor at the Scripps Institution of Oceanography at the University of California, San Diego, recommends drinking plenty of water, staying indoors if possible, and seeking out air-conditioned spaces, like local cooling centers. “Wearing lightweight, breathable clothing can help reduce heat strain,” Choi said.

But it’s also up to communities themselves to offer solutions, Choi pointed out. “As extreme heat events become more common, we need to shift from reactive emergency responses to proactive infrastructure and health planning,” she said. 

Edited by Health with a background in health, science, and investigative reporting. Previously, she wrote full time about parenting issues for the app Parent Lab. Before that, she worked as a reporter for National Geographic covering wildlife crime and exploitation." tabindex="0" data-inline-tooltip="true"> Jani Hall Jani Hall Jani Hall is a news editor for Health with a background in health, science, and investigative reporting. Previously, she wrote full time about parenting issues for the app Parent Lab. Before that, she worked as a reporter for National Geographic covering wildlife crime and exploitation. learn more

This story originally appeared on: Health News - Author:Brian Mastroianni