Frequent heatwaves are pushing human bodies to age faster

Sweltering heat does more than make people miserable. Repeated exposure to hot spells appears to push the body toward older biology in ways we can measure.

Biological age is not a birthday. It is a reading of how well the body’s systems are functioning. When that reading runs ahead of our calendar age, scientists call it biological age acceleration, and that gap tracks with higher risks of disease and earlier death.

Heatwaves make us age faster

A team working with health data from 24,922 adults in Taiwan found that more heatwave days over time lined up with faster biological aging.

This new work was led by Siyi Chen at The University of Hong Kong (HKU).

The first results focused on a two-year window of heatwave exposures before each participant’s health checkup and the link to their biological age recorded at those visits. This cohort that stretched from 2008 to 2022.

“Research now shows that exposure to heatwaves affects the rate at which we age,” said Paul J. Beggs, School of Natural Sciences at Macquarie University (MU).

Heat is not a niche problem. Many regions are already seeing longer, more frequent hot spells, and those patterns push health systems, workplaces, and vulnerable communities to their limits.

Understanding biological age

Biological age estimates how “worn” your body is compared with the average person of your calendar (chronological) age. Two 40-year-olds can have very different biological ages because bodies don’t wear at the same rate.

Scientists measure this “wear” with biomarkers – objective signs in your cells and blood.

Common ones include epigenetic clocks, telomere length, fitness measures like VO₂ max and grip strength, and blood markers tied to inflammation, glucose control, and lipids.

Your choices and environment push biological age up or down. Regular exercise, enough sleep, nutritious food, not smoking, and managing stress tend to slow aging signals; long-term stress, pollution, ultra-processed diets, and inactivity speed them up.

Some studies even show that improving lifestyle can make certain biomarkers “younger,” at least for a while. Put together, these data predict health risks better than birthdays do.

Biological wear and tear

For this particular study, the researchers estimated biological age using common clinical markers that reflect inflammation, blood pressure, and organ functions. This approach is well established in aging science and has been refined with large biobank data.

They calculated biological age acceleration as the difference between a person’s biological age and their birthday age. A higher number means a body that behaves older than the calendar suggests.

They then paired each person’s aging number with the heat they had faced.

The team built measures of cumulative heatwave exposure in the two years before each screening, including the total number of heatwave days and the intensity of those events.

More hot days meant faster aging

Each interquartile range increase in cumulative heatwave exposure was associated with a 0.023 to 0.031 year rise in biological age acceleration.

That is about 8 to 11 days of extra biological aging for the amount of heat that separates the middle half of exposures in the population.

The total number of heatwave days stood out as the most important driver. Intensity mattered too, but simple counts of hot days carried the strongest signal in this dataset.

The cohort showed some adaptation over the 15 year span, yet the aging effect remained. The pattern suggests communities can adjust, but heat still leaves a mark that adds up over time.

How heatwaves speed up age

Heat is a physiological stress that forces cells to respond. Heat shock proteins help keep other proteins from misfolding and assist in repair when temperatures climb.

Sustained heat can also raise oxidative stress and cause DNA damage. Those hits accumulate across tissues and nudge multiple systems toward older states.

Biological age acceleration captures this broad wear and tear. It rolls many signals into a single number that tracks future health risk more closely than birthdays do.

US studies confirm heatwaves and age link

The Taiwan findings match results in older American adults. A national US analysis used blood based epigenetic clocks to test the link between outdoor heat and aging in 3,686 people.

Short and mid term windows of more heat days aligned with higher PhenoAge acceleration by about 1.07 years, while longer windows showed a 2.48 year rise for one clock and consistent increases across other clocks.

“These findings provide insights into the biological underpinnings linking heat to aging-related morbidity and mortality risks,” wrote Eun Young Choi, University of Southern California.

Smarter ways to stay cool

Access to air conditioning lowers immediate heat risks, but it also releases added heat outside.

A seven city Japanese study estimated that AC use can prevent a large share of heat related deaths while a small fraction of deaths may be attributable to the extra outdoor heat it creates.

That tradeoff points to better cooling strategies, not less protection. More shade, reflective roofs, better building ventilation, and efficient cooling lower indoor temperatures while cutting waste heat and power demand.

Policies should follow the data. Manual workers saw around three times the aging impact for the same heat exposure, and rural residents with fewer air conditioners were also hit harder.

This research shows that protections must prioritize those groups with targeted cooling and work practice changes.

The study is published in Nature Climate Change.

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