Extreme heat may cause biological ageing faster than smoking or alcohol. New research shows that prolonged exposure to high temperatures could have harmful effects, especially for older adults. Scientists are raising alarms as global temperatures rise and heatwaves become more frequent.

A study published in Science Advances found that seniors who are often exposed to extreme heat show signs of accelerated biological ageing. Researchers from the University of Southern California (USC) analyzed data from over 3,600 people aged 56 and older across the United States. They compared these people’s biological markers with local temperature data. The results are concerning.

The Study: Heat and Ageing

The study suggests that people living in areas with temperatures regularly exceeding 32°C (90°F) experienced faster biological ageing. In some cases, their biological age increased by over a year due to frequent exposure to heat.

Biological age is different from chronological age. While chronological age counts how long someone has been alive, biological age shows how the body has aged on a cellular level. When biological age surpasses chronological age, the risk of serious health problems rises, including heart disease, diabetes, and even early death.

To measure biological age, the scientists used blood samples from people who participated in the study. The blood samples were taken between 2010 and 2016, from people in hot regions like Arizona. The researchers used epigenetic clocks, which are tools that track changes in DNA over time, to estimate biological age.

When the researchers compared biological age data with local heat trends, they found a link. People in hotter climates had faster biological ageing. Even after adjusting for habits like exercise, smoking, and alcohol use, the results showed that heat played a significant role in speeding up ageing.

What Is Biological Ageing?

Chronological age is simple—it counts the years a person has lived. But biological age tells a different story. It looks at how well the body functions and how cells and tissues wear down over time. A higher biological age means the body is ageing faster than the number of years lived. This can lead to health issues like higher blood pressure, cognitive problems, and a higher risk of diseases.

For the study, the researchers measured biological age using epigenetic clocks. These clocks track DNA changes that accumulate over time. Epigenetic clocks give a better understanding of how the body is ageing, compared to just counting years.

The Heat-Humidity Link

High temperatures are harmful, but humidity makes things worse. Humidity reduces the body’s ability to cool down. When it’s hot and humid, sweat evaporates more slowly. This makes it harder for the body to regulate its temperature.

Jennifer Ailshire, a professor at USC, led the study. She explained that as we age, our bodies sweat less efficiently. This makes older adults more vulnerable to heat stress. In hot, humid weather, the risk is even higher. The combination of both heat and humidity is particularly dangerous for seniors.

Ailshire pointed out that to understand the full risk of heat exposure, we need to consider both temperature and humidity. This dual threat is something that must be taken into account when planning for climate change impacts.

Climate Change and Older Adults

Global temperatures are rising. The World Meteorological Organization reports that 2024 was the hottest year on record, with temperatures about 1.6°C higher than pre-industrial levels. Heatwaves are becoming more frequent and more intense, posing serious risks to vulnerable groups, especially older adults.

Research links extreme heat to several health problems, including heart issues, kidney disease, and cognitive decline. The World Health Organization (WHO) estimates that heat causes over 175,000 deaths annually in Europe. Without action, the WHO warns that climate change could lead to an additional 2.3 million deaths in Europe by 2099.

This latest study highlights that older populations may be more at risk than previously thought. With rising temperatures, it’s possible that heat could significantly affect biological ageing and the overall health of older adults.

What Can Be Done?

Experts agree that steps must be taken to protect vulnerable groups from extreme heat. As the planet warms, we must rethink how cities are designed to cope with rising temperatures. Older adults are particularly at risk, so it is crucial to shield them from heat-related health dangers.

To combat the effects of extreme heat, experts recommend increasing urban green spaces, planting more trees, and creating buildings that are more heat-resistant. These measures can help keep cities cooler and reduce the risks of heat exposure.

“Climate change and an ageing population are a deadly combination,” Ailshire warns. “If we don’t act soon, the consequences could be severe.”

Preparing for the Future

This study shows how critical it is to address the health risks posed by extreme heat. As global temperatures continue to rise, the elderly will face more significant risks. Protecting older adults from heat stress should be a top priority for cities, governments, and health organizations.

In the future, more research will be needed to better understand how heat exposure affects biological ageing. But for now, this study is a clear call to action. The rising temperatures due to climate change could lead to a dangerous increase in biological ageing for seniors. If we are to protect our aging population, we need to plan and act now.

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