Are heatwaves fast-forwarding the ageing process?

We’ve always known that heatwaves are dangerous — they can cause dehydration, heatstroke, and even death. In fact, more Australians die from extreme heat than from any other natural disaster. But a surprising new study suggests they may be doing something even more insidious: quietly speeding up the way our bodies age.

The study that made waves

A long-term study of nearly 25,000 adults in Taiwan has revealed a startling connection between heatwaves and biological ageing. Over 15 years, researchers tracked health markers like blood pressure, organ function, and inflammation to estimate each person’s “biological age” — how old their body seems beyond the number of birthdays they’ve celebrated.

The results? Just four extra heatwave days over two years was enough to make the average person’s body age by about nine extra days. Outdoor workers were hit harder — their biological age increased by 33 days, over a month’s worth of ‘extra age’ from the relentless sun.

While a few days here and there might seem minor, scientists stress that over decades, this effect could accumulate into a serious health burden. Higher biological age is linked to greater risk of chronic illnesses and early mortality—similar to that caused by smoking, heavy drinking, poor diet, or lack of exercise.

You can read the full study in Nature Climate Change here: Repeated heatwaves can age you as much as smoking or drinking.

Why heat hurts more than you’d think

Heatwaves strain almost every system in the body: the heart pumps harder, organs work overtime, dehydration sets in, and inflammation kicks off cellular stress. Over time, these repeated pressures can damage DNA and speed up ageing on a cellular level.

And it’s not just a few scorching days that matter — it’s the accumulated number of hot days that has the biggest impact. The more heatwaves someone experiences over time, the faster their biological clock ticks.

Why Australians should pay attention

Australia already has some of the world’s hottest summers, and climate change is only making them worse. Heatwaves are becoming more frequent, longer, and more intense — especially in cities like Melbourne, Sydney, and Adelaide.

For older Australians, the reality is even more worrying. We already know that older people face higher risks of hospitalisation and death during heatwaves. Now, this study suggests that surviving a heatwave may leave a lasting mark on health, potentially accelerating ageing and the progression of age-related conditions.