The year 2023 was reported as the hottest year on record for planet Earth, and experts predict that by the middle of the 21st century, the United States will experience between 27 to 50 days per year with temperatures exceeding 90 degrees. Prolonged exposure to such high temperatures can lead to various heat-related illnesses, with potential complications including an increased risk of heart disease. A study revealed that high heat exposure may harm the body’s immune system and increase inflammation, consequently affecting cardiovascular health. Researchers emphasized the importance of understanding the effects of heat on health in order to develop strategies to prevent and mitigate the adverse impacts of climate change on well-being.
In 2020, the U.S. Bureau of Labor Statistics reported about 2,330 cases of illness or injury caused by heat exposure, with approximately 40 working adults dying each year from extreme heat exposure. This highlights the significant impact of high temperatures on human health, especially for individuals with outdoor jobs who are regularly exposed to heat. The new study conducted by University of Louisville researchers explored the effects of heat exposure on heart health and immune-inflammatory activation. The findings, presented at the American Heart Association’s Epidemiology and Prevention│Lifestyle and Cardiometabolic Scientific Sessions 2024, revealed a relationship between high temperatures and increased inflammation levels in the blood, potentially contributing to cardiovascular disease development.
The study recruited 624 adults with an average age of 49.5 years, analyzing blood samples for cytokine levels linked to inflammation as well as various types of white blood cells. Participants visited study sites in the Louisville, KY area during the summer, with each day having a median temperature of 76 degrees Fahrenheit. Researchers found that for every five-degree increase in the Universal Thermal Climate Index (UTCI), there was a corresponding increase in key markers of inflammation in the blood samples. Additionally, participants experienced a decrease in B cells, indicating reduced immune system capabilities, which could potentially increase vulnerability to disease and inflammation during high temperatures.
Although heat exposure is a well-known risk factor for cardiovascular disease, the study aimed to investigate the mechanisms through which high temperatures may contribute to immune-inflammatory activation. The research results suggest that even moderate levels of heat exposure can lead to changes in inflammation, as well as innate and adaptive immune responses. Dysregulation of the immune system and inflammatory pathways are known to play a significant role in various types of cardiovascular disease, indicating that heat exposure could potentially elevate the risk of developing heart-related issues. While the study provides valuable insights, experts caution that further research with better randomization and statistical analysis is necessary to confirm the findings and address any bias or confounders.
Cardiologists interviewed about the study acknowledged the known negative effects of heat stress on cardiovascular health and the role of inflammation in heart disease. Dr. Cheng-Han Chen emphasized the significance of the study in directly linking changes in inflammatory markers in response to short-term heat stress situations. To protect oneself from high heat exposure, Dr. Chen recommended staying indoors in air-conditioned environments, avoiding direct sunlight, staying hydrated, and wearing loose-fitting clothing. The study contributes to a better understanding of the impacts of heat exposure on heart health and underscores the importance of developing evidence-based approaches to address climate-related health risks.
