Exposure to heat can disrupt the immune system and lead to inflammation.
- In case of high heat, the body can trigger inflammation.
- This disrupts the functioning of the immune system.
- This can increase the risk of developing certain diseases, particularly cardiovascular diseases.
Sweating, fatigue, drowsiness or even exhaustion: extreme heat is often difficult to bear, particularly for people working outdoors. However, high temperatures have other consequences, more difficult to perceive. The American Heart Association presents the results of a study on disorders of the immune system linked to exposure to heat.
Heat and the immune system: abnormal inflammation of the body
Inflammation, caused by the body’s exposure to heat, interferes with the normal functions of the immune system in the body, which can increase susceptibility to infections and accelerate the progression of cardiovascular disease. “Inflammation is a normal part of the body’s defenses against injury or infection, however, an inflammatory response that is prolonged – weeks to months – or occurs in healthy tissue is damaging and plays a key role in the buildup of plaque in the arteries, which can lead to atherosclerosisdevelop the authors in this press release. Heat waves are known to promote inflammation, however, studies examining air temperature and biomarkers of inflammation have had mixed results.”
In this new work, the team of researchers used alternative measurements of heat, taking into account different markers of inflammation and immune response in the body.
How to observe the effects of heat on the immune system?
624 people participated in this trial. During the summer months, they visited the study site regularly to carry out blood tests. Next, the researchers ran analyzes to identify markers of immune system function, then compared that data with heat levels. The team used a metric called the Universal Thermal Climate Index (UTCI), which takes effective temperature into account.
“For every 5 degree increase in UTCI (in this study, the equivalent of going from a day without heat stress to a day with moderate heat stress), there was an increase in levels of key markers of heat stress. “inflammation: monocytes (4.2%), eosinophils (9.5%), killer T cells (9.9%) and tumor necrosis factor alpha (7%) in the blood”, they observe. The activation of these different immune molecules indicates that there is a rapid, nonspecific inflammatory response throughout the body. At the same time, a drop in B cells was noted: this means that the body’s adaptive immune system, which remembers specific viruses and germs and creates antibodies to fight them, has been lowered. For the authors, even low exposure to these temperatures can have consequences on the immune system.
Heat and immune system: a challenge for years to come
“With global temperatures rising, the association between heat exposure and a temporarily weakened immune system response is a concernunderlines Daniel W. Riggs, lead author of this study. During the hottest days of summer, people may be at greater risk of heat exposure, they may also be more vulnerable to illness or inflammation.” The people most at risk from high temperatures are those aged over 60 and those suffering from cardiovascular diseases.