Intense heat changes our biology and can make us age much faster

New research explores the pressing question of how extreme heat affects humans. The findings are concerning.

- Rongbin Xu and Shuai Li

Heat takes it out of you. After a long, hot day, we feel tired and grumpy.

But sustained periods of heat do more than that—they age us faster. Cumulative heat stress changes our epigenetics—how our cells turn on or off gene switches in response to environmental pressure.

Now, new research from the US explores the pressing question of how extreme heat affects humans. The findings are concerning. The more days of intense heat a participant endured, the faster they aged. Longer periods of extreme heat accelerated aging in older people by more than two years.

As the climate heats up, humans will be exposed to more and more heat—and our bodies will respond to these stresses by aging faster. These findings are especially pertinent to Australia, where heatwaves are expected to become more frequent and intense in a warmer world.

HOW, EXACTLY, DOES HEAT AGE US?

Aging is natural. But the rate of aging varies from human to human. As we go through life, our bodies are affected by stresses and shocks. For instance, if we don't get enough sleep over a long period, we will age faster.

While heat can directly sicken or kill us, it also has a long tail. Sustained heat stresses our bodies and makes them less efficient at doing the many jobs needed to stay alive. This is what we mean when we say it accelerates biological aging. This deterioration is likely to precede the later development of diseases and disabilities.

What does that look like on a genetic level? You might think your genes don't change over your life, and this is mostly true (apart from random mutations).

But what does change is how your genes are expressed. That is, while your DNA stays the same, your cells can switch some of its thousands of genes off or on in response to stresses. At any one time, only a fraction of the genes in any cell are turned on—meaning they are busy making proteins.