Living through extreme heat waves can accelerate your rate of aging, according to research published Monday.
Scientists analyzed 15 years’ worth of health data from nearly 25,000 adults in Taiwan and found that two years of exposure to heat waves could speed up a person’s so-called biological aging by eight to 12 extra days.
It may not sound like a lot, but this number builds over time, said Cui Guo, an assistant professor at the University of Hong Kong who led the study, which was published Monday in the journal Nature Climate Change.
“This small number actually matters,” she said. “This was a study of a two-year exposure, but we know heat waves have actually been occurring for decades.”
The research comes as human-induced climate change is making heat waves more intense and long-lasting. The West Coast of the United States is suffering from sweltering temperatures while Iran is experiencing searing heat. Record-breaking temperatures punished Europe, Japan and Korea earlier this month. France recently experienced its second heat wave of the summer, sparking a national debate over air-conditioning.
In 2024, the hottest year on record, climate change was responsible for 41 extra days of extreme heat worldwide, according to an analysis by World Weather Attribution.
Particular groups are more vulnerable to faster aging because of heat, the researchers found. If you’re an older person who has lived through many heat waves, you may age faster than a younger person who had the same exposure, Dr. Guo said. Other factors, such as living without air-conditioning or working outdoors, can also make your aging rate significantly worse.
Dr. Guo cautions this isn’t the same as losing literal days off your life; it reflects a measurable shift in biological aging markers, not the calendar.
The study defined heat waves as both a period of at least two consecutive days of abnormally high temperatures as well as any time when officials issued heat warnings. It also took the sum of a person's heat exposure into account.
The researchers quantified the heat’s effects by comparing people’s biological age to their chronological age. Biological age, is a measure of how healthy a person’s lungs, liver and cells are compared with a perfectly healthy person, Dr. Guo said.
The study used 12 of these health measurements, known as biomarkers, to calculate how heat affected the rate of aging for the study’s participants. The results accounted for individual factors that can affect aging markers, such as exercise, smoking and preexisting disease.
“Most countries are facing an aging population,” Dr. Guo said. Since biological aging is closely linked to death and many diseases, speeding it up can be an indicator of serious health problems.
The population of Taiwan, along with Italy, Spain and Hong Kong, ranks as one of the oldest in the world. In the United States, a little less than a quarter of the population is expected to be 65 or older by 2050.
The research published Monday builds on other studies that have found similar detrimental health effects of heat exposure. A recent analysis of 3,600 older Americans found that living in 90 degrees Fahrenheit for at least 140 days a year could cause up to 14 months of additional aging.
Unlike the study in Taiwan, the research in the United States did not account for some individual factors that might affect health, like smoking. Kristie Ebi, a professor at the University of Washington who was not involved in either study, said that such factors make a large health impact, and accounting for them is key to correctly analyzing the effects of heat on a population.
Other long term changes can make a difference too, Dr. Ebi said. Over a period as long as 15 years, a population may slowly acclimate to hotter temperatures, including finding new ways to cope with heat. The authors of the Taiwan study suggested that a moderate increase in the number of households with air-conditioners correlated to diminished aging from heat over time.
“The results may have implications for public health interventions,” said Dr. Ebi, noting that there are ways that governments can intervene to protect people in a warming world.
For example, residents of Oregon can use Medicaid funding to buy an air-conditioner if they have health conditions that can get worse in hot weather, she said. But air-conditioners should not be considered an ideal solution because the energy they use can make the outside air hotter and contribute to climate change, Dr. Ebi said.
Extreme heat can also present other, less direct risks to health. High temperatures have been found to worsen air quality, and set the stage for other disasters, such as wildfires, drought and storms.
“People just have low awareness that heat kills or that, in this case, has adverse health consequences,” Dr. Ebi said. “That’s just been a persistent challenge.”