Coco Liu | Bloomberg News (TNS)

Cardiovascular-related deaths due to extreme heat are expected to nearly triple in the U.S. by mid-century as climate change raises the frequency of very hot days, according to a new study. Older and Black adults are likely to be the most affected.

The study, supported by the National Institutes of Health and published Monday in the journal Circulation, predicts that the number of heat-related cardiovascular deaths in the contiguous U.S. will increase from an annual average of 1,651 recorded in recent years to 4,320 by mid-century (defined as from 2036 to 2065).

Although extreme heat poses a universal threat to health, older and Black adults are expected to be disproportionately impacted because of chronic illness and socio-economic challenges, such as living without air conditioning.

Exposure to high temperatures stresses the cardiovascular system, forcing the heart to work harder. That, in turn, increases the odds of having a heart attack, stroke or other life-threatening episode, especially for people with heart disease.

“The health burdens from extreme heat will continue to grow within the next several decades,” Sameed Khatana, the study’s co-author and an assistant professor of medicine at the University of Pennsylvania, said in a statement. “Due to the unequal impact of extreme heat on different populations, this is also a matter of health equity and could exacerbate health disparities that already exist.”

Khatana and his co-authors made their projection by first evaluating county-level data from the contiguous 48 U.S. states during summer months from 2008 to 2019 to set a baseline. They also examined the connection between extreme heat — days with a heat index of 90F (32.2C) or higher — and cardiovascular mortality. Humidity levels, which can influence body temperatures, were also taken into consideration, as well as projected population changes.

The team modeled how heat would increase using a middle-of-the-road climate emissions projection and calculated how that would affect mortality. The death toll could rise further to 5,491 people if emissions rise sharply, the authors note.

Khatana and his co-authors call for infrastructure upgrades to help communities adapt to a hotter future. Their paper is the latest of a series of warnings from medical professionals about how excessive heat can trigger a variety of health problems and amplify existing inequalities. Last summer, the record-breaking temperatures in Europe caused more than 60,000 premature deaths, according to a study published in July.

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