Extreme heat can be particularly dangerous for older people, putting them at increased risk for heat stroke and death. But could it also affect how their DNA functions, and accelerate the aging process itself?

A new study, published Wednesday in the journal Science Advances, suggests it could. The analysis of over 3,600 older adults in the United States found that those living in neighborhoods prone to extreme heat — classified as 90 degrees or above — showed more accelerated aging at a molecular level compared with those in areas less prone to extreme heat.

The findings suggest that heat waves and rising temperatures from climate change could be chemically modifying people’s DNA and speeding up their biological aging. The study authors estimated that a person living in an area that reached 90 degrees or above for 140 days or more in a year could age up to 14 months faster than someone in an area with fewer than 10 extreme heat days a year.

To conduct the study, the researchers analyzed three biomarker aging estimates, known as epigenetic clocks, which were derived from blood samples of people age 56 and older as part of a separate national population study. They then looked at these age estimates alongside six years of daily climate data, comparing them across geographies.

Epigenetic clocks measure biological changes that could predict the future risk of disease or death associated with older age. They estimate “how well the body is functioning at the molecular and the cellular level,” said Eun Young Choi, a postdoctoral associate at the U.S.C. Leonard Davis School of Gerontology and a co-author on the paper. While DNA is fixed at birth, external factors like stress or pollution can trigger molecular changes that turn genes on and off and affect how they operate. “DNA is like a blueprint,” Dr. Choi said, but these epigenetic changes are like the “switchboard that controls which part of the blueprint gets activated.”

This is the first population-level analysis to establish a connection between heat exposure and epigenetic aging in humans, building on separate research finding similar changes in fish, mice and guinea pigs.