Living in extreme heat can make you age faster, study finds

Get the air conditioner ready

Many of us hate being hot, but according to a new study, prolonged exposure to extreme heat could speed up our biological ageing.

Bad news for those of us regularly sweltering in the heat, on top of making us irritable, tired, sweaty and uncomfortable, the extremely hot weather could also speed up our biological aging, according to a new study.

Researchers from the University of Southern California analysed blood samples from more than 3000 people aged over 56 in the US. 

They used a biochemical test called an epigenetic clock to estimate participants’ biological age, before comparing them to their area’s heat index.

The gerontologists determined that people who had lived in extremely hot states such as Arizona on average had a higher biological age than those living in colder areas like Washington State. They categorised ‘extremely hot’ as over 32 degrees, and said living in this climate for over 140 days a year could add up to fourteen years to residents’ biological age.

Co-author Eun Young Choi claimed the effects of extreme heat were seen across different demographics, saying "even after looking at other factors — age, sex, ethnicity, education — this magnitude we found is comparable to the effects of smoking."

She noted that the increase was only temporary in people living in hot areas for a short period of time, but addressed how the impact of prolonged exposure to extreme heat may not be immediately evident. 

The gerontologists determined that people who had lived in extremely hot states such as Arizona on average had a higher biological age than those living in colder areas like Washington State. Image: Pexels

"The effects of this extreme heat might not show up right away as diagnosable health conditions," she said. "But they could be taking a silent toll at the cellular or molecular level.

"So, over time, this biological deterioration could accumulate and eventually, years later, lead to disability and disease."

Professor of social epidemiology at Harvard T.H. Chan School of Public Health, Nancy Krieger, wasn’t involved in the study, but said it is an “important, suggestive work” as many of the states mentioned in the study as having some of the hottest days “are also some of the states that have the worst health profiles.”

However, she highlighted that the study didn’t account for lifestyle factors which could also influence biological ageing. 

Many of the states mentioned in the study as having some of the hottest days “are also some of the states that have the worst health profiles.” Image: Pexels

What do the findings mean for Australians?

Many areas around Australia definitely see temperatures above 32 degrees regularly.

Choi said, "The real-world consequences of [heat] exposure can vary significantly depending on local infrastructure, climate conditions and other available resources."

Though the co-author said the findings could pertain to other countries, some experts question if the type of testing used can really determine the impact of heat on our bodies.

Thermoregulatory physiologist Ollie Jay from the University of Sydney also wasn’t involved in the study, but told the ABC the researchers “used the heat index, which incorporates humidity, but this is only useful in hot-humid climates where the environment is restricting sweat evaporation."

"In very hot and dry climates, sweat freely evaporates, but there still can be significant thermal strain because heat loss is limited by the ability to produce sweat."

Though the co-author said the findings could pertain to other countries, some experts question if the type of testing used can really determine the impact of heat on our bodies. Image: Pexels

He emphasised the importance of looking at thermoregulation factors in this type of analysis, saying there are better ways to measure heat strain. 

“[They] incorporate not just the climate but activity, clothing and physiological restrictions to thermoregulation”.

Choi agreed that more research is needed to determine if exposure to extreme heat really does accelerate biological aging, saying “There are many factors at play and some individuals might be more resilient or have ways to reduce their heating."

Originally published as Living in extreme heat can make you age faster, study finds