Many Americans choose to head to the South for its promise of warm, sunny winters. 

The appeal, especially for retirees, is obvious: Relaxing in the sun with time for leisure activities, beach visits and long walks are daily occurrences in some of the most popular retirement states. 

But a new study has found the great American migration could actually have deadly consequences.

It’s no surprise that constant sun exposure can spur on wrinkles and cause spotting on your skin. But research suggests it’s the heat – not just the rays – that can cause even more, initially less visible, damage: biological aging.

In recent years, the US has seen hundreds of thousands of residents relocate to Texas, Florida and North Carolina. Experts have told the Daily Mail this likely has to do with tax rates, but they’re also places with generally desirable weather.

The former two, in addition to Louisiana, Mississippi, Alabama, Georgia and Arizona, showed up as the highest risk states when it comes to heat-caused damage, according to a study out of the University of Southern California – those states were exposed to more days of extreme heat.

Dr. Eun Young Choi and her team of researchers specifically focused on 3,686 Americans over the age of 56 from 2010 – 2016. The study was published in the journal Science Advances.

They found that prolonged exposure to high temperatures appeared to noticeably speed up biological aging, and people who live in hotter states are more likely to be affected.

Older adults appeared to be at the greatest risk from long-term heat exposure, with temperatures in the 80s leading to accelerated aging

The study examined how heat affects our cells on a molecular level, ultimately concluding that heat causes them to wear out sooner than they naturally would in a cooler climate. 

This increased wear and tear can raise the risk for ailments that come with age, including heart disease and kidney dysfunction, in addition to the changes on our skin, of course. 

Ultimately, the research is showing that your relocation could end up costing you a few years of your life, rather than extending it like you might assume the lower stress and sunnier skies might be able to do for you.

What is biological aging?

The concept of age exists on multiple planes: chronological (think, your annual birthday celebration), mental, emotional and biological.

When someone says their grandkids keep them young, they’re likely talking about feeling much younger, cognitively, than their chronological age of, let’s say, 85.

And we’ve all experienced a friend saying their date had the emotional maturity of a four-year-old.

But when it comes to biological age, the most common way we might be able to understand this is the concept of ‘dog years’: Man’s best friend ages at a quicker pace than humans do, which is why one human year (365 days) is often equated to around 7 dog years (still 365 days, but the cells have aged as much as a human would in 2,555 days).

The things determining our biological age are our cells and how they change over time. Many factors – including habits like drinking alcohol and smoking – can affect the pace. 

‘While we don’t yet have the same level of causal evidence as we do for smoking and alcohol, the results highlight that heat exposure is not just a short-term health hazard,’ Dr. Choi told the Daily Mail.

How does the sun wear out our cells? 

Some scientists believe high heat (above 80 or 90 F) alters and disrupts the chemical markers in our bodies – which act like switches, turning different genes on and off. 

These changes can linger and cause long-term damage to the immune system or spark inflammation, which is a known trigger of biological aging.

Over a six-year period, participants in Dr. Choi’s study who spent more of their days in the temperature range’s ‘extreme caution’ level (90 – 103 F) showed biological aging that was 2.88 years ahead of their actual age.

The study found that participants who spent more than 140 days in such an environment during a single year saw a biological age increase of up to 14 months.

American living in the South faced the largest number of extremely hot days, putting them at the greatest risk for experiencing accelerated aging

Americans in all of Louisiana and Mississippi spent over three years living in danger-level conditions (103 – 124 F) during the six-year study (pictured: Bay St. Louis, Mississippi) 

Large portions of Texas, Oklahoma, Arkansas and Alabama were in the same zone for more than half of the study’s duration. (Pictured: Oklahoma City)

 ‘The key concern with accelerated biological aging is that it reflects cumulative stress on the body, which can increase the risk of age-related diseases,’ said Dr. Choi, who is also a postdoctoral associate at New York University.

‘Prior research has linked accelerated epigenetic aging to higher risks of cardiovascular disease, metabolic disorders, cognitive decline and even mortality,’ she added.

Dr. Choi’s team used three different ‘aging clocks’ to help detect the changes in DNA patterns that come with aging (or methylation): PCPhenoAge, PCGrimAge and DunedinPACE.

Each of the metrics measured a different part of this aging-by-heat process.

PCPhenoAge predicted age-related health declines over time, PCGrimAge was used to determine each person’s risk of death throughout the study, and DunedinPACE measured the pace of biological aging in real-time.

According to PCPhenoAge, even as little as a week of exposure to moderately warm temperatures can start causing age-related changes in the body. The effect was worse among elderly Americans.

The danger zones

Although there wasn’t a single region of the US free of caution-level heat, the greatest threat to human health was centered in the South.

Americans in all of Louisiana and Mississippi spent over three years living in danger-level conditions (103 – 124 F) during the six-year study.

Large portions of Texas, Oklahoma, Arkansas and Alabama were in the same zone for more than half of the study’s duration.

Meanwhile, Americans in Florida, Missouri, Georgia and Illinois spent more than a year of their lives baking in 100 F heat.

Choi isn’t asking people to avoid these states, but she did stress the need to keep cool any way possible, including using air conditioners at home and making changes that combat global warming at a state level.

‘We can’t just tell people to pack up and move to a cooler place. Heat exposure varies widely, even within the same state or neighborhood,’ she explained.

‘Two people living on the same street could have very different experiences depending on factors like air conditioning, access to cooling centers or whether they work outdoors.’

So, what can you do?

Dr. Choi explained that the artificial ways many people heat themselves up – like regularly using a sauna or taking extremely hot showers – likely won’t cause you to age prematurely. In fact, short bursts of heat may actually be healthy.

‘Some research suggests that short-term heat exposure, such as sauna use, can have benefits for circulation and cardiovascular health,’ she said.

However, the doctor recommends people who love the heat stay hydrated and find an adequate place to cool down to avoid long-term exposure.

She stressed that brief exposure ‘may have neutral or even beneficial effects in some cases,’ it’s sustained or repeated exposure we should be conscious of, ‘especially in vulnerable populations.’

So if you’re considering getting away from the cold – or even the cool – think twice about where you land, and how long you plan to stay.