Heatwaves may be speeding up your biological ageing, study warns

Repeated exposure to heatwaves appears to accelerate ageing in people, with detrimental effects comparable to smoking, alcohol consumption or a lack of exercise, a new study suggests.

Previous evidence has linked heatwaves to short-term spikes in deaths, for example, nearly 600 premature deaths during a single heatwave in England this year. But the new findings, published in Nature Climate Change, reveal the longer-term consequences.

The research analysed 15 years of health data from nearly 24,922 adults in Taiwan, who had an average biological age of 46 years.

The study concluded that just four extra days of heatwave exposure over two years was associated with an increase in biological age of roughly nine days.

Researchers used routine medical markers - blood pressure, inflammation markers, cholesterol and measures of lung, liver and kidney function - to calculate each participant’s “biological age” and then modelled how that age changed with heatwave exposure.

The study found that manual labourers, rural residents and people in communities with limited air-conditioning in particular were more vulnerable to heatwave-related ageing. Simply, those living in areas with more hot days tended to show greater biological ageing than people in cooler regions.

The study advised people to take steps to cope with the heat, such as using air conditioning where available and spending more time in the shade.

“If heatwave exposure accumulates for several decades, the health impact will be much greater than we have reported,” said Dr Cui Guo, at the University of Hong Kong, who led the study.

“Heatwaves are also becoming more frequent and lasting longer so the health impacts could be much greater [in the future]”.

What is a heatwave and how does it affect our bodies?

A heatwave is an extended period of unusually high temperature, defined relative to local climate thresholds rather than a single universal temperature. For example, in the UK, the Met Office declares a heatwave when daily highs exceed regional thresholds for three or more consecutive days - typically 25°C in cooler areas such as Wales and Scotland, and 28°C in hotter zones including London and parts of the East Midlands.

In the short term, extreme heat places immediate stress on the body’s cooling systems. Sweating and increased blood flow to the skin help regulate temperature, but these responses place extra stress on the heart and kidneys. And if fluids and rest are insufficient, this can result in dehydration, heat exhaustion, and in severe cases, potentially fatal heatstroke.

Over the long term, repeated or prolonged exposure to high temperatures can worsen chronic health conditions, including cardiovascular, respiratory, and kidney diseases.

Scientists believe that cumulative cellular damage - including DNA damage, oxidative stress, and chronic inflammation - may explain why frequent heat exposure appears to accelerate biological ageing.

Why this matters now

The new findings come amid a global climate crisis that is making heat waves longer, hotter, and more frequent. In particular, sweltering temperatures are affecting Europe, the fastest-warming continent on Earth. France has already endured two record-breaking heat waves this summer, with temperatures rising above 43 degrees Celsius in certain parts of the country.

One recent assessment from World Weather Attribution, an international network of researchers,* calculated an average of about 41 additional days of dangerous heat globally in 2024.

The death toll caused by heat is already severe. Almost 63,000 heat-related deaths occurred across Europe during summer 2022, according to researchers. Prolonged, repeated exposure - the new study warns - may add a quieter, cumulative burden.

The International Labour Organization estimates more than 2.4 billion people are exposed to workplace heat stress, with heat contributing to over 22 million occupational injuries and nearly 19,000 work-related deaths each year.

Europe’s Pan-European Commission on Climate and Health - a group convened by WHO Regional Director Dr Hans Kluge - warns that extreme weather is now “a public health emergency unfolding in real time”.

The new study highlights the need for policies that reduce environmental inequalities and strengthen heatwave resilience, particularly for vulnerable populations. It also calls for targeted protection and efficient healthcare planning.