The research comes as human-induced climate change is making heatwaves 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 this month. France recently experienced its second heatwave 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 ageing because of heat, the researchers found. If you’re an older person who has lived through many heatwaves, you may age faster than a younger person who had the same exposure, Guo said. Other factors, such as living without air conditioning or working outdoors, can also make your ageing rate significantly worse.
Guo cautions this isn’t the same as losing literal days off your life; it reflects a measurable shift in biological ageing markers, not the calendar.
The study defined heatwaves 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, Guo said.
The study used 12 of these health measurements, known as biomarkers, to calculate how heat affected the rate of ageing for the study’s participants. The results accounted for individual factors that can affect ageing markers, such as exercise, smoking and pre-existing disease.
“Most countries are facing an ageing population,” Guo said. Since biological ageing is closely linked to death and many diseases, speeding it up can be an indicator of serious health problems.
The population of Taiwan, 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 3600 older Americans found that living in 90 degrees Fahrenheit for at least 140 days a year could cause up to 14 months of additional ageing.
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 analysing the effects of heat on a population.
Other long-term changes can make a difference too, 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 ageing from heat over time.
“The results may have implications for public health interventions,” said 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, 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,” Ebi said. “That’s just been a persistent challenge.”
This article originally appeared in The New York Times.
Written by: Sachi Kitajima Mulkey
Photographs by: Jordan Vonderhaar
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