It’s a well-known fact that spending long hours under the sun is bad for your health.

As well as the risk of headaches and heat stroke, sun exposure dramatically increases the chance of skin cancer, with 70% of skin cancer cases linked to sun exposure.

But now researchers have added two more serious harms to the list: heart disease and immune system destruction.

Scientists at the University of Louisville in Kentucky found that just one day in a hot outdoor environment can increase the telltale signs of inflammation in the body by at least 10%.

Some of these signs – the release of inflammatory compounds that cause a spiral of internal damage – are clearly associated with the buildup of plaque in the arteries that causes heart disease.

Researchers at the University of Louisville in Kentucky studied 624 adults who had their blood drawn during the summer months of May 2018 to September 2019.

The study also showed a 6 percent decrease in important immune system cells called B cells, which help the body fight viruses and bacteria.

In this study, 624 adults underwent a single blood draw during the summer months from May 2018 to September 2019.

On the day the participants visited the clinic for their blood test, their average body temperature was 76 degrees Fahrenheit (24.5 degrees Celsius).

Researchers analyzed blood tests for multiple markers to show how well a person’s immune system was functioning.

The researchers were specifically looking at levels of important compounds such as T cells, B cells, and cytokines (signaling molecules that can cause inflammation), which are released when the immune system detects injury.

We then looked at the association of markers with heat levels, including temperature that takes into account humidity, air temperature, wind speed, and net effective temperature.

We also compared the Global Heat Climate Index (UTCI), which takes into account temperature, humidity, wind speed, and UV levels.

They found that natural killer T cells increased with every 5 degree increase in UTCI, suggesting that inflammation is occurring in the body.

According to the researchers, this difference corresponds to days with no heat and days with moderate heat stress.

Participants’ blood had a 10 percent increase in killer T cells, which activate the immune system and trigger an inflammatory response in the body to protect against pathogens and injury.

Inflammation is part of the body’s normal defense against infection, but a long-term, consistent inflammatory response (lasting weeks to months) or an inflammatory response that occurs in healthy tissue can be damaging and lead to plaque buildup in the arteries. plays an important role in the accumulation of .

This can lead to the development of coronary artery disease and heart attack.

Researchers also found a 7 percent decrease in B cells, indicating a decrease in the part of the immune system that remembers certain viruses and produces antibodies to fight them. Suggests.

“While our study participants were exposed to only a small amount of high temperature on the day of their blood test, even small exposures can contribute to changes in immune markers,” said the study’s authors. said lead author Daniel Riggs, assistant professor at the University of Louisville School of Medicine.

Prof Riggs added that adults aged over 60 and those with existing cardiovascular disease are particularly at risk of heat-related cardiovascular events and death.

“As global temperatures rise, the association between heat exposure and a temporary reduction in immune system response, as temperature and humidity are known to be important environmental factors for airborne infections. There are concerns about gender.”

“Thus, during the hottest days of summer, people may be at increased risk of heat exposure and may also be more susceptible to illness and inflammation.”