NIH Record - National Institutes of Health

Hazards of Climate Change

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Extreme heat is projected to increase cardiovascular deaths. Older and Black adults are at higher risk.


Cardiovascular-related deaths due to extreme heat are expected to increase between 2036 and 2065 in the U.S., according to an NIH-supported study. The researchers, whose work is published in Circulation, predict that adults ages 65 and older and Black adults will likely be disproportionately affected.

While extreme heat currently accounts for less than 1% of cardiovascular-related deaths, the modeling analysis predicted this will change because of a rising heat index. Older adults and Black adults will be most vulnerable because many have underlying medical conditions or face socioeconomic barriers that can influence their health—such as not having air conditioning or living in locations that can absorb and trap heat, known as “heat islands.”

To generate these predictions, researchers evaluated county-level data from the contiguous 48 states between May and September 2008-2019. More than 12 million deaths related to cardiovascular disease occurred during that time. Using environmental modeling estimates, they also found the heat index rose to at least 90 degrees about 54 times each summer. Researchers linked the extreme temperatures during each summer period to a national average of 1,651 annual cardiovascular deaths. 

Using modeling analyses to forecast environmental and population changes, the researchers looked to 2036-2065 and estimated that each summer, about 71 to 80 days will feel 90 degrees or hotter. Based on these changes, they predicted the number of annual heat-related cardiovascular deaths will increase 2.6 times for the general population, assuming greenhouse gas emissions are kept to a minimum. If emissions rise significantly, deaths could more than triple.

For older adults and Black adults, the projections were more pronounced. Among those 65 and older, deaths could almost triple, increasing from 1,340 to 3,842 if greenhouse gas emissions remain steady—or to 4,894 if they don’t. Among Black adults, deaths could more than triple, rising from 325 to 1,512 or 2,063.

Study author Dr. Sameed Khatana of the University of Pennsylvania said, “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.

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