Many of us treat heat waves as a short-term annoyance. We close the blinds, crank up the fan and hope the electric bill will not be too shocking at the end of the month. But new research suggests that every spell of extreme heat could also be quietly pushing our bodies along the aging curve.
A large study published in Nature Climate Change followed 24,922 adults in Taiwan for fifteen years and found that repeated heat waves accelerate biological aging, in a way comparable to long-term smoking or regular alcohol use.
The effect on any single person looks small at first glance. Over two years of frequent heat waves, people accumulated about eight to twelve extra days of biological age. Yet when you scale that across whole populations living through hotter summers year after year, the implications for public health become hard to ignore.
Biological age, not just the number on your ID
The researchers were not counting wrinkles or grey hair. They calculated each volunteer’s biological age from medical tests that capture how well key organs and systems are working. That included measures of liver, kidney and lung function, blood pressure, cholesterol and markers of inflammation.
They then compared this biological age with each person’s chronological age and used the difference as a measure of biological age acceleration. In simple terms, they asked whether someone’s body looked older or younger than the age on their ID card.
Heat waves were mapped using local weather records and defined as several days in a row with unusually high temperatures for that region. Over the study period from 2008 to 2022, Taiwan experienced around thirty of these events.
When the team grouped people by how much heat they had faced, a clear pattern appeared. Moving from one exposure group up to the next was linked to an extra 0.023 to 0.031 years of biological age, which works out to roughly eight to eleven days.
That may sound modest, but the study authors note that this effect size is similar to well-known risk factors such as smoking, heavy drinking, poor diet or lack of exercise.
Heat waves are multiplying as the planet warms
Scientists have long warned that climate change is making hot extremes more frequent and intense. The latest assessment from the Intergovernmental Panel on Climate Change concludes that it is virtually certain that hot extremes and heat waves have increased in both frequency and duration since the middle of the 20th century, largely because of human-driven warming.
Recent analyses from the World Weather Attribution network add a stark global snapshot. Between mid-2024 and mid-2025, about four billion people experienced at least thirty extra days of extreme heat that would have been far less likely without human-caused climate change.
Put together with the Taiwan findings, that means the background climate is now exposing billions of people to a new kind of chronic risk. The danger is not only the dramatic, headline grabbing spikes in heat-related deaths during a record breaking summer.
It is also the slow, almost invisible wear on hearts, blood vessels, kidneys and brains as biological aging speeds up year after year.
Workers, rural residents and people without cooling pay the highest price
One of the most striking results in the Taiwan study is who suffers the most. Manual workers, rural residents and people living in communities with fewer air conditioners showed stronger links between heat exposure and accelerated aging.
It fits what many people already feel in daily life. A construction worker on a sun-baked street, a farm laborer in the fields or a delivery cyclist stuck in traffic without shade cannot duck into an air-conditioned room whenever the temperature spikes. Their bodies absorb hour after hour of heat stress, summer after summer.
Heat also interacts with existing health problems. The study and related research suggest that repeated thermal stress can worsen cardiovascular strain, disrupt metabolic regulation and increase the risk of chronic diseases such as heart disease, diabetes, kidney failure and even dementia. For the most part, people do not feel that damage in the moment. It shows up years later as a shorter healthy lifespan.
Interestingly, the researchers did see signs that populations were adapting. Over the fifteen year follow up, the impact of heat on biological aging weakened somewhat.
They suspect wider access to cooling technologies and better awareness of heat risks may play a role, although the exact reasons remain unclear. Even so, adaptation is uneven. Air conditioning protects those who can afford the device and the power bill, while others are left to cope with fans, open windows and hope.
Turning down the heat on an aging planet
What can be done in practical terms? At the city level, simple measures such as planting trees, creating shaded bus stops and designing cooler building materials can lower urban heat and ease the burden on vulnerable residents.
Public health agencies can expand heat alert systems, open cooling centers and check on older people who may be living alone in small apartments that trap hot air long into the night.
Workplace rules also matter. Enforcing rest breaks, access to drinking water and flexible schedules during extreme heat can protect outdoor workers whose livelihoods depend on staying active even when the pavement shimmers.
At the end of the day, though, these adaptation steps are only part of the story. The same fossil fuel emissions that drive climate change and make heat waves more likely are also setting the stage for this quiet acceleration of aging.
Cutting greenhouse gas emissions is not only about saving polar ice or distant ecosystems. It is about protecting the years of healthy life in our own communities.
The study was published in Nature Climate Change.