People dealing with prolonged extreme heat exposure can appear older and even have their genes altered, according to a new study published in Science Advances.

The study assessed over 56 people living across the United States (US) with different heat experiences from extreme to very mild.

According to an NPR news report, the study found that the impact of extreme heat (like that of Phoenix where NPR says temperatures there topped 90 degrees Fahrenheit for a record-breaking 188 days) is “similar to the effect of smoking and drinking”.

It found that residents living in cooler parts of the country where there were fewer days of intense heat looked about 14 months biologically younger than those in hotter areas.

Biological or epigenetic ageing differs from chronological ageing or birthdays and instead deals with DNA and how chemical tags build up and are then lost from people’s DNA over time, the report explained. This can change how our genes operate.

The scientists assessed the DNA of residents and found that poor eating, poor exercise habits and even environmental stressors like prolonged extreme heat can cause this process to speed up.

“The outcomes were clear. People who experienced more heat over the long term aged faster, biologically, than those living in cooler places. That’s even after taking into account people’s financial status, education, physical activity and whether they smoked,” the report said.

Tom Clanton, a physiologist and heat expert at the University of Florida’s College of Health and Human Performance, who wasn’t involved in the research told NPR, “At the genome level, heat exposure makes you sort of accelerate your way towards an old heart, and an old vulnerable heart.”