Heart disease: Extreme heat may drive inflammation, increasing risk

Evan Walker
Evan Walker TheMediTary.Com |
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A new study reports heat exposure may harm the immune system and increase inflammation, potentially impacting heart health. Martin Harvey/Getty Images
  • 2023 was the hottest year on record for planet Earth, and by the middle of the 21st century, the U.S. will experience 27–50 days of temperatures exceeding 90 degrees each year.
  • Prolonged heat exposure may lead to heat-related illnesses with complications such as increased risk for heart disease.
  • A new study reports that high heat exposure may harm the body’s immune system and increase inflammation, potentially harming a person’s cardiovascular health.

Scientists reported that 2023 was the warmest year on record for planet Earth, and the world’s median temperature is increasing much more rapidly than it was at the start of the 20th century.

If this warming trend continues, experts believe that by the middle of the 21st century, the United States will experience between 27 to 50 days of over 90 degrees each year.

Almost 33% of working adults in the U.S. have a job where they are regularly exposed to the outdoors, including heat.

In 2020, the U.S. Bureau of Labor Statistics reported about 2,330 cases of illness or injury caused by heat exposure. And each year, about 40 working adults die from extreme heat exposure.

Prolonged exposure to high heat can lead to several heat-related illnesses, including:

  • heatstroke
  • heat exhaustion
  • heat cramps
  • heat headaches
  • heat rash
  • sunburn

“Additionally, exposure to heat can also lead to further complications. For example, heat can negatively impact pre-existing cardiovascular disease.”

A new study reports that high heat exposure may harm the body’s immune system and increase inflammation, potentially harming a person’s cardiovascular health.

The findings were recently presented by University of Louisville researchers at the American Heart Association’s Epidemiology and Prevention│Lifestyle and Cardiometabolic Scientific Sessions 2024. The study results have yet to be published in a peer-reviewed journal.

This study also found that study participants experienced a decrease in B cells, which researchers say also indicates a lowering of the capabilities of the body’s immune system.

“Temperature and humidity are known to be important environmental drivers of infectious, airborne disease transmission,” Dr. Riggs said.

“This could suggest that not only are people at higher risk of exposure to infectious disease during high temperatures, but they could also be more vulnerable to disease or inflammation.”

“Dysregulation of the immune system and inflammatory pathways are known to be a leading mechanism in many types of cardiovascular disease,” he continued.

“Our findings suggest that heat exposure could be contributing to these pathways that ultimately lead to greater risk of cardiovascular disease.”

After reviewing this study, Dr. Justin Lee, an interventional cardiologist at Hackensack University Medical Center in New Jersey told MNT he felt the authors propose an interesting hypothesis that may warrant further research with better randomization and statistical analysis.

“Interesting hypothesis; however, there are much stronger cardiovascular disease risk factors — i.e., cigarette smoking, obesity, hypertension, diabetes, high cholesterol, family history — that have proven evidence with robust cause and effect relationship,” Dr. Lee explained.

“It does not appear that the authors in the study conduct thorough sample analysis and propensity matching to ensure true randomization of the subjects. Hence, the results are not immune to bias and confounders.”

MNT also spoke with Dr. Cheng-Han Chen, a board-certified interventional cardiologist and medical director of the Structural Heart Program at MemorialCare Saddleback Medical Center in Laguna Hills, CA, about this study.

“We have known for a long time that heat stress has negative effects on someone’s Health, including cardiovascular Health,” Dr. Chen said.

“We’ve also known that inflammation in the body also has effects on cardiovascular Health. This study is useful because it directly ties changes in inflammatory markers in the bloodstream of patients in response to these short-term heat stress situations. So it makes sense that that would be so, but it’s good to have the data showing this.”

— Dr. Cheng-Han Chen, cardiologist

To protect yourself from high heat exposure, Dr. Chen recommended the following:

  • try to stay indoors and in an air-conditioned environment as much as possible
  • stay away from direct sunlight
  • drink plenty of water
  • wear loose-fitting clothing

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