Disastrous heat

High temperatures cause people to age faster

People who lived in a very hot region within one year or within six years appeared "older" due to their epigenetic characteristics.

(Bild: Goffkein - stock.adobe.com)

Periods of heat not only cause acute damage to people: US researchers have also found evidence that extreme temperatures also accelerate biological ageing.

"Heat is known to strain the heart and kidneys and slow down cognitive abilities. But extreme heat can also have effects that are - at least initially - invisible," wrote "Nature" author Heidi Ledford in the corresponding study. This was recently presented at the annual meeting of the American Society for Gerontology (ageing research) in Seattle.

"The physical consequences may not show up immediately as a visible health effect, but may affect our bodies at the cellular and molecular level," said study co-author Eun Young Choi, a gerontologist at the University of Southern California in Los Angeles. "And this biological decline could later develop into disability."

(Bild: stock.adobe.com/Wolfilser)

DNA methylation patterns characteristic of biological age
The scientists used the so-called "epigenetic clock" as a benchmark. This is a whole collection of chemical changes in people's DNA that accumulate with increasing age. Specifically, it is methylation, i.e. the attachment of methyl groups to certain parts of the genetic material. "The pattern of DNA methylation, a specific epigenetic mark, changes in ageing cells. The epigenetic clock can be used to determine a person's biological age (...)", stated the German Max Planck Institute for Biology of Ageing.

The US scientists have now analyzed the "epigenetic clock" of around 3800 people aged 56 and over. "They then compared this data with temperature maps of the United States and looked for correlations between the status of molecular markers and the number of days in different time periods when the heat index - a measure of perceived temperature that takes into account both heat and humidity - exceeded either 26.7 degrees Celsius or 32.2 degrees Celsius at the participant's location," it was reported in "Nature".

Ten percent more heat days - 0.12 years biologically "older"
 It was found that people who lived in a very hot region within a year or within six years appeared "older" than people without these heat experiences due to their epigenetic characteristics. "In one measurement, every ten percent increase in the number of hot days extended the molecular age of the participants by 0.12 years. Analysis of another set of molecular markers showed that people who lived in hot regions aged up to 0.6 percent faster. However, shorter heat exposure in the range of days or months did not correlate with differences in these markers," wrote "Nature" author Heide Ledford.

"This is a remarkable result," explained Danish environmental epidemiologist Rina So (University of Copenhagen). For the first time, biological markers from the blood had been used for such an investigation instead of simply linking deaths or illnesses to climate influences. The US researchers statically adjusted for other possible influencing factors such as social stress, other environmental influences, pregnancies and additional health factors.