Extreme Heat Could Make Older Adults Age Faster by Altering Their DNA, Study Finds
Researchers compared genetic markers of aging to daily temperature records in areas across the United States and found that elderly people exposed to more hot days showed more rapid biological aging
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Extreme heat can increase the risk of cardiovascular disease, affect mental health and worsen asthma. And those negative health effects are particularly dangerous to elderly people: Now, a new study suggests extreme heat could even alter the DNA of older adults and accelerate biological aging.
A pair of researchers at the University of Southern California analyzed blood samples from more than 3,600 adults over the age of 55. Their analysis found that those living in neighborhoods with frequent hot days showed faster biological aging than those living in cooler areas. Their findings were published in late February in the journal Science Advances.
“This is one of the first large-scale studies to link long-term heat exposure to biological aging in humans,” study lead author Eunyoung Choi says to New Scientist’s Carissa Wong.
The research team focused on “epigenetic clocks”—measurements of chemical modifications to people’s DNA as they grow older—as a proxy for aging. Although scientists debate whether these are the most accurate measure of aging, the markers are often used to estimate “how well the body is functioning at the molecular and the cellular level,” Choi says to Mohana Ravindranath at the New York Times.
A person’s biological age might not always match up to their chronological age—and a higher biological age can raise the risk of aging-related diseases.
The researchers cross-referenced these epigenetic clocks with temperature data from across the United States in the six years before the blood samples were collected in a 2016 study. They found that someone living in an area with more than 140 extreme heat days per year—defined as days that surpass 90 degrees—could age up to 14 months faster than someone living in a cooler area with fewer than ten extreme heat days annually.
The study accounted for race and ethnicity, as well as physical activity, education, income, smoking, obesity and alcohol consumption. “Two people that had identical sociodemographic characteristics and similar lifestyles, just because one is living in a hotter environment, they experience additional biological aging,” says Choi to ABC News’ Julia Jacobo.
“It’s important, suggestive work,” Nancy Krieger, an epidemiologist at the Harvard T.H. Chan School of Public Health who was not involved in the study, tells the New York Times. Many of the places with the most extreme heat days “are also some of the states that have the worst health profiles.”
When it comes to extreme heat, older adults are especially at risk, since aging decreases the body’s ability to regulate its temperature. Certain medications taken by elderly people can also interfere with their tolerance for heat, writes Choi in an article for the Conversation.
But heat is not necessarily the only factor that may be leading to negative health outcomes—and the study only establishes a link between extreme heat and biological age, not a causal relationship. The research also doesn’t account for all the ways in which people might protect themselves from heat, like using air conditioning or staying indoors.
“What is clear, however, is that extreme heat is more than just an immediate health hazard—it may be silently accelerating the aging process, with long-term consequences for public health,” Choi writes in the Conversation.
Future research can examine what other factors might make someone more vulnerable to faster biological aging, says senior author and gerontologist Jennifer Ailshire in a statement, which can then inform public health policies. She hopes that cities’ infrastructure will be updated to reflect the importance of heat-resilient areas, such as by including shaded bus stops and sidewalks, planting more trees and increasing green space.
“If everywhere is getting warmer, and the population is aging and these people are vulnerable, then we need to get really a lot smarter about these mitigation strategies,” Ailshire adds.
