WORLDWIDE — Short-term exposure to higher heat could increase inflammation and interfere with normal immune system functions in the body, a recent study found. This might, in turn, increase susceptibility to infections and accelerate the progression of cardiovascular disease.

The study involved 624 adults and was conducted by the Christina Lee Brown Envirome Institute at the University of Louisville in Louisville, KY.

Inflammation is a normal part of the body’s defenses against injury or infection. However, an inflammatory response that lasts weeks to months, or one that occurs in healthy tissues, is damaging and plays a key role in the build-up of plaque in the arteries. This could lead to atherosclerosis. 

“Most research only considers temperature as the exposure of interest, which may not be adequate to capture a person’s response to heat,” said lead study author Daniel Riggs, Ph.D., an assistant professor of medicine in the Envirome Institute. “In our study, we used alternative measurements of heat in relation to multiple markers of inflammation and immune response in the body to investigate the short-term effects of heat exposure and produce a more complete picture of its health impact.”

To measure physical comfort, the study factored in temperature, humidity, wind speed and ultraviolet radiation levels. This was compared to blood tests that checked immune-function markers. 

The analysis found that for every five-degree increase in thermal stress, there was an increase in the levels of certain markers of inflammation and a decrease of 6.8 percent in B-cells.

“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,” said Riggs. “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.”

Adults older than age 60 and adults with existing cardiovascular disease are particularly at risk for heat-related cardiovascular events and deaths, he added.

For full details, links to multimedia and more, visit www.newsroom.heart.org/news/heat-exposure-may-increase-inflammation-and-impair-the-immune-system. 

Contributed by the American Heart Association.