Sunbathing for just one day ‘increases your risk of killer heart disease – and wrecks your immune sys...

IT'S no secret that baking your body in the sun is not the best idea when it comes to your health.

Aside from the risk of sunburn or heatstroke, you can also increase your chances of developing skin cancer.

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When it comes to your skin, dermatologists have told The Sun that there's no safe way to tan because even a hint of bronzing is equivalent to sun damage.

Now, research shows that languishing under the sun's scorching rays could also increase your risk of heart disease and hamper your body's immune response.

Scientists from the University of Louisville found that just one day spent in hot weather was enough to drive up markers of inflammation in the body.

Inflammation, which is associated with heart disease risk, is part of the body's normal response to infection or injury.

But long-term inflammatory responses that last weeks or months, or which occur in healthy tissues, can be damaging and fuel buildup of plaque in the arteries.

This can in turn lead to atherosclerosis, a thickening or hardening of the arteries that can increase your risk of heart attack and stroke.

The research was presented the American Heart Association's Epidemiology, Prevention, Lifestyle and Cardiometabolic Health conference in Chicago, but hasn't been published in a scientific journal yet.

Lead by epidemiologist and professor of environmental medicine Dr Daniel Riggs, the team looked at blood samples taken from 624 people who were part of the Louisville Green Heart Project, which is studying how planting greenery in neighbourhoods might improve air quality and reduce heart disease.

Participants aged 20 to 70 years old visited study sites in Louisville during the summer months of 2018 and 2019 for a blood test, which researchers analysed for markers of how well the immune system was performing.

The average temperature on the days participants visited the clinics time period was 24.5 degrees Celsius (76 degrees Fahrenheit).

Researchers specifically looked at at levels of key compounds released by the immune system when it detects injury, like cytokines - molecules that can trigger inflammation.

The cytokines and immune cells were used to show how much the body ramped up its defences in response to a perceived threat.

Results showed a link between hot weather and increased levels of several cytokines.

The association between heat exposure and a temporarily weakened response from the immune system is a concern

Dr Daniel RiggsEpidemiologist and professor of environmental medicine

One of them, TNF-alpha, is "one of the major inflammatory markers and plays an important role in cardiovascular disease," Dr Riggs said.

Hot weather was associated with higher levels of white blood cells known as monocytes and killer T-cells, which could be a sign that heat is causing inflammation or prompting an immune response, Dr Riggs went on.

Researchers also noticed a decrease in an infection-fighting and blood-cleansing white blood cell known as B cells.

According to Dr Riggs, lower levels of these cells could mean someone is more susceptible to infection.

The team found that the warmer the weather, the more there was an increase in inflammatory markers.

Dr Riggs told the conference he was surprised to see so many types of cells change with the short-term exposure to hot weather. 

“Our study participants only had minor exposure to high temperatures on the day of their blood test, however, even minor exposure may contribute to changes in immune markers,” he explained.

Those most at risk

It's already known that people are at risk of heat-related cardiovascular events and deaths, particularly those over the age of or with an existing cardiovascular disease.

Dr Riggs said: “With rising global temperatures, the association between heat exposure and a temporarily weakened response from the immune system is a concern because temperature and humidity are known to be important environmental drivers of infectious, airborne disease transmission.

"Thus, during the hottest days of summer people may be at higher risk of heat exposure, they may also be more vulnerable to disease or inflammation.”

He advised people to reduce their exposure to heat and the sun during hot weather by staying indoors when temperatures are highest and the sun is strongest.

Seeking out shade when you're out and about, wearing light, breathable clothing and drinking plenty of water can also help.