As climate change drives more frequent and intense heat events, a critical question emerges: what does chronic heat exposure actually do to the body over time? A study published in Science Advances demonstrates that prolonged heat exposure may accelerate biological aging at the molecular level.

While the adverse effects of heat on health and mortality are well documented among older adults, this study is the first to directly link neighborhood level heat exposure to biological aging - examining what sustained heat does to older adults' bodies before it ever becomes a medical emergency.

Researchers took blood samples from more than 3,600 U.S. adults age 56 and older, collected over a six-year period as part of an ongoing longitudinal study, to look at biomarkers associated with aging. Researchers then compared those results to historical weather data in participants’ neighborhoods.

The results found that older adults living in neighborhoods that regularly reached 90 degrees or above were more likely to experience accelerated aging at a molecular level compared with those living in cooler neighborhoods.

“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,” said Jennifer Ailshire, lead author of the study and professor of gerontology and sociology at the USC Leonard Davis School. “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.”

Biological age is a measure of how well the body functions at the molecular, cellular, and system levels, as opposed to chronological age, which is based on birthdate.

It’s important to note the study used heat index – a measurement that combines the air temperature and relative humidity to determine how hot it actually feels to the human body – rather than just air temperature.

“It's really about the combination of heat and humidity, particularly for older adults, because older adults don't sweat the same way," Ailshire explained. “We start to lose our ability to have the skin-cooling effect that comes from that evaporation of sweat.

“If you’re in a high humidity place, you don’t get as much of that cooling effect,” she said. “You have to look at your area’s temperature and your humidity to really understand what your risk might be.”

If you are personally experiencing a heat wave, there are steps you can take to keep yourself safe.

• ‍Dress for the heat. Wear light-weight clothing. If you are in danger of overheating, get your clothing damp. 
• ‍Take a cool bath or shower. Or use a cold wash cloth or ice pack to cool your body.  ‍
• Drink fluids. Water or an electrolyte drink is best. Avoid caffeinated beverages if possible.   ‍
• Rest in a cool place. Turn on the AC in your home or vehicle. Or visit a public air-conditioned building such as a shopping mall, library, or movie theater. ‍
• Look for signs. Signs that you need medical attention include headache, dizziness, cool clammy skin, or excessive sweating. If you experience any of these, don’t hesitate to call for help. 

For more information on aging and extreme heat please take alook at these sources:

• ‍Heat and Older Adults (Aged 65+)
• 8 Types of Medications that can make it harder to handle the heat
• Heat Stress: Warning Signs

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