Heat Waves Could Accelerate Biological Aging, Study Suggests

By analyzing health data from nearly 25,000 adults in Taiwan, researchers discovered that two years of exposure to heat waves could accelerate biological aging by up to 12 days.

“This study confirms that sustained heat exposure can cause subtle but long-term biological changes associated with aging, shedding light on how climate change and extreme weather patterns may affect public health in the future,” says the lead author Cui Guo, PhD, an assistant professor of urban planning and design at the University of Hong Kong.

How Researchers Measured the Effects of Heat on Aging

For the new study, researchers compared the chronological and biological ages of participants using about 15 years of health data.

To gauge each person’s biological age, they relied on several biomarkers (measurable signs of how well the body functions) identified via blood tests, analyses of liver function and inflammation, and other criteria. They also accounted for individual factors that can influence aging, such as smoking, chronic conditions, and exercise.

Heat waves are typically understood as “an extended period of unusually high temperatures lasting several consecutive days,” Dr. Guo says. For this study, Guo and her team defined a heat wave as any period of two or more consecutive days of exceptionally high heat, and any days that officials announced heat warnings.

Using these factors, they calculated participants’ total heat exposure, including the number of heat wave days, how long heat waves lasted, and cumulative temperature.

The study found that long-term exposure to heat waves was closely linked with “acceleration of the biological aging process,” Guo says. “Every additional four days of heat wave exposure was associated with a biological age increase equivalent to about nine days.”

Overall, the team found that two years of exposure to heat waves increased biological aging by 8 to 12 days, the study says.

What We Already Know About the Effects of Heat on Health

The research adds “another line of evidence in terms of the detrimental impact of heat exposure,” says Amir Sapkota, PhD, a professor and the chair of epidemiology at the University of Maryland School of Public Health in College Park. Dr. Sapkota, who was not involved in the Taiwanese study, is a researcher focused on climate change and health.

While the new study doesn’t directly suggest heat exposure shortens lifespan, Guo says its potential to accelerate aging may increase the risk of age-related diseases and early death.

“Even modest increases in biological age, if accumulated over time, could have meaningful implications for public health, especially among vulnerable populations,” she says.

Some Groups Are More Affected by Heat Exposure

The new study highlighted that certain groups, including rural residents, manual workers, and people living in communities with fewer air conditioners are more vulnerable to the effects of heat waves, Guo says.

The Study Has Some Limitations

People in the study tended to be healthier and more educated, Guo says, which could potentially skew the findings.

The study also didn’t factor in detailed individual data, such as how much time someone spent outside or how much access they had to cooling systems, she says. Heat exposure was also estimated at a community level based on residential address and outdoor temperature, rather than individually. This may have introduced some exposure misclassification, Guo notes.

She suggests that future research should examine how individuals adapt to heat waves long-term and the effectiveness of air-conditioning and other cooling methods in protecting health.

How to Stay Safe During Periods of Extreme Heat

• Drink plenty of water to stay hydrated.
• Seek out cool spaces.
• Use air-conditioning if you have it.
• Minimize physical activity outdoors.
• Plan outdoor activities to avoid the hottest times of day.
• Wear light, loose-fitting clothing.

“Extreme heat can be fatal,” says Sapkota, adding that heat waves are becoming more common and more intense, and are lasting longer. “We will continue to see extreme heat events for the foreseeable future, and this is very concerning from a health perspective.”