How heatwaves are making people age faster – Firstpost

Heatwaves are no longer just temporary episodes of discomfort; scientists are uncovering how they silently shape long-term human health.

Beyond immediate dangers such as dehydration and heatstroke, new research shows that sustained exposure to extreme heat speeds up the body’s biological ageing.

The findings are reshaping the medical and public health understanding of climate-related risks, placing heatwaves alongside smoking, alcohol, and poor diet as major contributors to accelerated ageing.

How are heatwaves linked to biological ageing?

Biological age is different from the number of years a person has lived. It is calculated through physiological measures such as inflammation levels, organ function, cholesterol, blood pressure, and markers of cellular health.

When biological age outpaces chronological age, it suggests the body is deteriorating more quickly, increasing vulnerability to chronic diseases and early mortality.

Researchers from the University of Hong Kong, working with long-term data from nearly 25,000 adults in Taiwan, tracked how exposure to heatwaves correlated with biological ageing.

Over a 15-year study period published in Nature, they measured participants’ health through regular screenings and compared the results with the number of hot-weather days they endured.

The analysis revealed a clear pattern: the more heatwaves people lived through, the faster their biological age advanced.

The data showed that an additional four days of heatwave exposure over two years corresponded to an increase of approximately nine days in biological age.

For outdoor workers and manual labourers, the effect was much more pronounced, with biological age increasing by more than a month in the same conditions.

People living in rural regions also faced disproportionate impacts, likely due to reduced access to cooling technologies such as air conditioning.

“The physiological changes in the body associated with ageing can appear earlier and progress faster in some people than in others,” explained Paul Beggs of Macquarie University in Australia, reflecting on the findings.

Until now, heatwaves were mostly studied for their short-term consequences. Sudden spikes in temperature are known to trigger surges in hospital admissions and excess deaths. For instance, a heatwave in England in June was linked to nearly 600 premature deaths.

Europe’s record-breaking summer of 2022 saw almost 63,000 heat-related fatalities, highlighting how extreme heat is already among the deadliest weather phenomena.

What this new research shows is that the health effects extend far beyond immediate casualties. Prolonged exposure to extreme heat does not simply end when the weather cools — it leaves lasting scars on the body, speeding up its biological clock.

Beggs underlined the significance of the findings: “Many of us have experienced heatwaves and survived unscathed – or so we thought. [This research] now shows that exposure to heatwaves affects the rate at which we age.”

He added, “In 2024, [scientists] discovered that early life heat exposure negatively impacts brain white matter development in children. Coupled with the new finding that heatwave exposure accelerates ageing in adults, we have a paradigm shift in our comprehension of the extent and gravity of heat’s impact on our health. The impact can occur at any age and can be lifelong.”

What are the long-term risks?

What makes the results striking is that the effect of repeated heat exposure appears comparable to long-established ageing accelerants.

Unhealthy habits such as smoking, excessive alcohol consumption, sedentary behaviour, and poor diet are all known to hasten physiological decline.

Now, prolonged periods of extreme heat are being recognised as another factor that can shave years off healthy lifespans.

“If heatwave exposure accumulates for several decades, the health impact will be much greater than we have reported,” said Dr Cui Guo of 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].”

The researchers stressed that while the immediate rise in biological age might look modest, the effect compounds over a lifetime. Even small increases, repeated year after year, translate into meaningful reductions in long-term health.

Higher biological age is strongly correlated with elevated risks of cardiovascular disease, kidney disorders, respiratory illness, and premature death.

How do heatwaves harm the body?

A heatwave is generally defined as a period of several consecutive days where temperatures remain unusually high compared to local norms.

For example,
in the UK, the Met Office sets thresholds of around 25°C in cooler regions and 28°C in hotter ones, measured over at least three days.

In the short term, excessive heat pushes the body’s cooling mechanisms to their limits. Sweating and increased blood flow to the skin help release heat but place added strain on the heart and kidneys.

Without enough hydration and rest, this can lead to dehydration, exhaustion, or potentially fatal heatstroke.

Over longer timescales, repeated exposure appears to inflict cellular and organ-level damage. Scientists point to mechanisms such as DNA damage, oxidative stress, and persistent inflammation as likely causes of accelerated ageing.

Who faces the highest risks?

The Taiwanese study revealed that the impacts of heat-induced ageing are not evenly distributed across populations.

Outdoor workers, including agricultural labourers and construction workers, face far greater risks due to prolonged time spent under the sun. Their biological age was found to advance more than three times faster than the general population under similar heat exposure.

Rural residents were also disproportionately affected. In many communities, access to air conditioning is limited, leaving people more exposed during heatwaves.

While cooling devices offer protection, experts caution that they are not a perfect solution.

“Air conditioners also directly add to the heat outdoors, making conditions for those without air conditioners even worse than they would have been,” said Beggs, urging the adoption of sustainable cooling systems instead.

The study also noted that its participants — who were enrolled in paid health management programmes — were generally younger, healthier, and more educated than the broader population.

This suggests that older individuals, those with pre-existing health conditions, or people with lower access to healthcare may face even greater risks than reported.

How is climate change complementing the problem?

The research comes against the backdrop of a rapidly warming planet. Climate change is increasing both the frequency and intensity of heatwaves. According to World Weather Attribution, an international scientific network, the year 2024 saw an average of 41 additional days of dangerous heat globally.

Fossil fuel emissions, which continue to reach record levels, are the primary driver of this escalation.

Europe
has emerged as the fastest-warming continent, enduring consecutive record-breaking heatwaves with temperatures climbing above 43°C in parts of France.

Asia, too, is experiencing devastatingly high temperatures, with entire regions facing weeks of unrelenting heat.

The health burden is already vast. The International Labour Organisation estimates that more than 2.4 billion people are exposed to occupational heat stress, contributing to over 22 million workplace injuries and nearly 19,000 deaths annually.

Why is this not a new crisis?

The Taiwanese study is not an isolated finding.

A recent US investigation found that outdoor heat contributed to accelerated ageing in older adults, while another analysis linked long-term heat exposure to faster cognitive decline in vulnerable populations, particularly among Black communities and residents of disadvantaged neighbourhoods.

Together, these studies highlight that the ageing effect of heat exposure is not confined to one region or demographic but is likely a global phenomenon.

“We now have at least two prominent studies showing an impact of heatwave exposure on ageing, with these examining populations from two different countries,” Beggs noted.

What is the solution?

Although the research showed that the negative effects of heat exposure diminished somewhat over time, they remained significant. This may indicate that people are adapting by changing behaviours, such as seeking shade or using cooling systems.

However, adaptation has limits, particularly as heatwaves grow hotter and more frequent.

Scientists stress that relying on air conditioning alone will not solve the problem. Apart from its contribution to outdoor heat, heavy use of air conditioning drives up energy consumption, reinforcing the cycle of climate change.

Researchers argue for sustainable alternatives, such as better urban planning, improved housing insulation, reflective surfaces, shaded public spaces, and green infrastructure that cools cities naturally.

Why is this a public health emergency in the making?

International health bodies warn that extreme weather is becoming one of the most urgent health threats of the century. The Pan-European Commission on Climate and Health, convened by the World Health Organisation, has declared that heat-related risks now represent “a public health emergency unfolding in real time.”

This recognition means that policymakers, healthcare providers, and communities will need to develop targeted strategies to protect vulnerable populations.

Strengthening resilience to heatwaves will require coordinated action across sectors, from labour protections and urban design to global climate commitments.

As Beggs summarised, “We all need to take heatwaves seriously – not only looking after our own health but also that of others in our communities.”

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With inputs from agencies