Projected Increase in Cardiovascular Deaths Due to Extreme Heat

Deaths related to cardiovascular disease due to extreme heat are expected to increase between 2036 and 2065 in the United States, according to a study supported by the National Institutes of Health. The researchers, whose work is published in Circulation , predict that adults aged 65 and older and black adults will likely be disproportionately affected.

While extreme heat currently accounts for less than 1% of cardiovascular disease-related deaths, model analysis predicted this will change due to a projected increase in summer days with a temperature of at least 32.22 degrees. This heat index , which takes into account how temperature feels with humidity, measures temperature extremes. Older adults and Black adults will be the 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 places that can absorb and trap heat, known as "heat islands. " heat" .

"Health burdens from extreme heat will continue to increase in the coming decades," said Sameed A. Khatana, MD, MPH, study author, cardiologist and assistant professor of medicine at the University of Pennsylvania, Philadelphia. "Due to the disparate impact of extreme heat on different populations, this is also a health equity issue and could exacerbate health disparities that already exist."

To generate these predictions, researchers evaluated county-level data from the lower 48 states between May and September 2008-2019. During that time, there were more than 12 million deaths related to cardiovascular diseases. Using estimates from environmental models, they also found that the heat index rose to at least 32.2 degrees about 54 times each summer. The researchers linked the extreme temperatures that occurred during each summer period to a national average of 1,651 cardiovascular deaths annually. Some areas, such as the south and southwest, were more affected than others, such as the northwest and northeast.

Using modeling analysis to forecast environmental and population changes, researchers looked at the period 2036-2065 and estimated that for 71 to 80 days each summer, the temperature will be 32.2 degrees or higher. Based on these changes, they predicted that the number of annual heat-related cardiovascular deaths will increase 2.6 times for the general population: from 1,651 to 4,320. This estimate is based on greenhouse gas emissions, which trap the sun’s heat, being kept to a minimum. If emissions increase significantly, deaths could more than triple, to 5,491.

For older adults and black adults, the projections were more pronounced. Among people aged 65 and older, deaths could nearly triple, rising from 1,340 to 3,842 if greenhouse gas emissions remain stable, or to 4,894 if they do not. Among black adults, deaths could more than triple, rising from 325 to 1,512 or 2,063.

When comparing current and future populations, researchers took multiple factors into account, including age, underlying health conditions and where a person lived.

Most people adapt to extreme heat as the body finds ways to cool itself, such as through perspiration. However, people with underlying health problems, including diabetes and heart disease, may have different responses and face higher risks of having a heart attack, irregular heart rhythm, or stroke.

"The number of cardiovascular events due to heat affects a small proportion of adults, but this research shows how important it is for those with underlying risks to take additional steps to avoid extreme temperatures," said Lawrence J. Fine, MD, senior advisor at the prevention and clinical applications branch, in the Division of Cardiovascular Sciences of the National Heart, Lung, and Blood Institute (NHLBI), part of the NIH.

The authors described cooling approaches that some cities are using: planting trees for shade, adding air-conditioned cooling centers, and using heat-reflective materials to pave streets or paint roofs. However, more research is needed to understand how these approaches may impact population health.

"In addition to thinking about the impact of extreme temperatures in the United States, this type of forecast modeling also foreshadows the impact that extreme heat could have around the world, especially in regions with warmer climates and that are disproportionately affected by health disparities," said Flora N. Katz, Ph.D., director of the Division of International Training and Research at the NIH Fogarty International Center.