Extreme heat can have devastating effects on the heart, and a recent report sheds light on the potentially deadly consequences of climate change in the United States. The study highlights the heightened vulnerability of black adults, seniors, and those residing in urban areas.
Between 2008 and 2019, the heat index, which factors in temperature and humidity, reached at least 90 degrees on an average of 54 days each summer in the US. These scorching days were associated with nearly 1,700 excess cardiovascular deaths annually, as revealed in a study published in the journal Circulation.
If global fossil fuel development continues to expand and minimal efforts are made to reduce planet-warming pollution, the researchers predict that the US could experience 80 days of extreme heat during every summer. This alarming scenario could result in over triple the number of heat-related cardiovascular deaths, reaching approximately 5,500 excess deaths each year.
Even with more plausible climate change mitigation measures in place, there could still be an increase in extreme heat, with 71 days per year and a 2.6 times rise in heart-related mortality. This would lead to over 4,300 excess cardiovascular deaths associated with excessive heat by the middle of the century.
Currently, heart disease is the leading cause of death in the US, and extreme heat accounts for only a small fraction of cardiovascular deaths, about 1 in every 500. However, as hot days become more frequent, the importance of risk mitigation intensifies, explains Dr. Lawrence Fine, a senior adviser at the National Institutes of Health’s National Heart, Lung, and Blood Institute, which partially funded the research.
“Heat-related deaths primarily occur during periods of extreme heat and predominantly affect individuals with underlying health conditions or other vulnerabilities,” says Dr. Fine. These heatwaves strain emergency rooms and the healthcare system, posing severe threats to certain individuals.
Hence, addressing the root causes of increasing temperatures and heart disease is essential, but it is equally important to raise awareness among vulnerable individuals and provide them with specific plans to cope with extreme heat environments.
The projections in the new study are based on estimates of population growth and migration in the US, along with trends in greenhouse gas emissions from a report by the United Nations’ Intergovernmental Panel on Climate Change. The analysis covers the years 2036 to 2065, using county-level data for the contiguous 48 states.
This summer serves as a grim reminder of the dangers of extreme heat. In Maricopa County, Arizona, officials reported 469 heat-associated deaths, with over 150 under investigation, making 2023 the deadliest year for heat-related fatalities since tracking began in 2006.
A significant number of these deaths occurred during record-breaking temperatures in the Southwest, where Phoenix experienced 31 consecutive days at or above 110 degrees Fahrenheit from June to July.
Heat-related fatalities have surged in recent years in the US, with over 1,700 deaths attributed to heat-related causes in 2022 alone, according to data from the US Centers for Disease Control and Prevention. Experts believe this figure is likely underestimated due to a lack of comprehensive documentation of extreme heat exposure.
The heart is particularly susceptible to the effects of heat. The human body operates within a narrow temperature range, and the heart plays a critical role in regulating this balance. Dr. Sameed Khatana, an assistant professor of cardiovascular medicine at Penn Medicine and senior author of the study, explains that when the heart is forced to work harder due to increased temperatures, the consequences can be fatal for individuals with pre-existing cardiovascular conditions.
Extended exposure to heat can lead to additional complications, such as increased inflammation and blood clotting, which raise the risk of heart attacks and strokes.
In the US, black adults face a higher risk of heat-related cardiovascular harm. According to the study’s projections, heat-related cardiovascular deaths among black adults could increase six-fold over the next few decades, compared to a projected 2.4 times increase among white adults in the worst-case scenario.
Seniors aged 65 and older and adults residing in metropolitan areas are also expected to be disproportionately affected. Demographic shifts in the US, including an aging population, urban growth, and diversification, could exacerbate these vulnerabilities.
Dr. Khatana emphasizes that addressing these health impacts of climate change and extreme heat requires targeted solutions for the most vulnerable individuals. Factors such as lack of tree cover and limited access to air conditioning may further compound the risks faced by vulnerable populations. Additionally, black individuals are more likely to live with conditions that increase their risk of heart problems, including higher rates of hypertension and diabetes.
“If efforts to reduce emissions and mitigate climate change are not pursued, then the existing health inequities may continue to widen,” warns Dr. Khatana.
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