Phoenix’s extreme heat is well-known for causing immediate health issues like heatstroke and heart problems. Last year, temperatures in the city soared above 90°F for a record 188 days, with more than 140 of those days exceeding 100°F. Now, a new study published in Science Advances shows that prolonged exposure to such heat can have long-term effects, accelerating aging at a molecular level and potentially impacting people’s health over time.
The research, led by Eunyoung Choi, a gerontologist at the University of Southern California, reveals that the impact of heat on aging is comparable to the effects of smoking and drinking. The study looked at people aged 56 and older from various regions of the U.S., comparing those who lived in extremely hot areas like Phoenix—where the heat index exceeded 90°F for half the year—to those in cooler cities like Seattle.
The findings were striking. People in hotter areas appeared biologically 14 months older, based on epigenetic changes, than those in cooler regions. While this might seem like a small difference, experts highlight the significant toll it takes on health. Deborah Carr, a gerontologist at Boston University, notes that this accelerated aging can lead to early-onset health issues like dementia, diabetes, and cardiovascular diseases, ultimately affecting quality of life and productivity.
The researchers tracked biological aging through changes in DNA, specifically focusing on methylation—a process that modifies how genes function without altering the DNA itself. DNA methylation patterns accumulate over time, providing a molecular clock for aging. Environmental stressors like heat exposure can accelerate this process, leading to faster biological aging.
The study found that people in hotter climates experienced faster epigenetic aging, even after accounting for factors like socioeconomic status, education, and lifestyle choices. This effect underscores the growing health risks tied to climate change, with rising temperatures expected to increase the frequency and severity of heatwaves.
As climate change continues to worsen, the number of extreme heat days in the U.S. could rise by 20 to 30 days by mid-century, according to the National Climate Assessment. Older adults, whose bodies are less efficient at regulating heat, are particularly vulnerable. Yet, the effects of heat are not limited to older individuals. Heat can strain the body’s physiological systems at any age, making it harder for everyone to maintain balance.
Researchers suggest the next step is to focus on how specific heat exposures—such as those experienced within homes—affect health outcomes. Personalized risk assessments could provide further insight into how heat accelerates aging and guide preventive measures.
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