At a glance
- Researchers estimate that between now and mid-century, deaths from cardiovascular disease will increase due to extreme heat.
- The projected increase is likely to disproportionately impact certain groups and widen health disparities.
Climate change due to greenhouse gas emissions is making heat events more frequent and intense in the United States. This trend is expected to continue in the coming decades. When the body cannot cool properly, dangerous heat-related illnesses such as heat exhaustion and heat stroke can occur. Extreme heat can have a more subtle, but still deadly, effect.
The cardiovascular system plays a central role in regulating body temperature. People with cardiovascular disease are at increased risk from extreme heat. An NIH-funded research team led by Dr. Sameed Katana at the University of Pennsylvania set out to estimate how increased heat waves would affect mortality rates from cardiovascular disease.
Researchers analyzed county-level data from 2008 to 2019 in the continental United States. They compared the number of deaths from cardiovascular disease and the number of summer days with a heat index of 90 degrees Fahrenheit or higher. Then, using models of future greenhouse gas emissions and socio-economic conditions, starting in 2036, he predicted the hottest days and county population in 2065. One model represented a middle-of-the-road scenario. This included slow population growth and climate policies that limited greenhouse gas emissions and stabilized global warming. Another model represented a worst-case scenario of rapid population growth and unchecked increases in greenhouse gas emissions. Their discovery is Circulation October 30, 2023.
Between the summers of 2008 and 2019, more than 12 million adults in the United States died from cardiovascular disease. The researchers estimated that an average of 1,651 (0.2%) of these deaths were associated with extreme heat each year. In a moderate scenario, the researchers estimated that this number would more than double to more than 4,300 by mid-century. In the worst-case scenario, excess deaths would more than triple to nearly 5,500.
Changes in excess mortality were not uniform across demographic groups. In the middle-of-the-road scenario, excess deaths among people aged 65 and older increased by 3.5 times compared to younger people. In the worst-case scenario, excess deaths among older people increased 2.9 times that among younger people. Excess deaths among non-Hispanic black adults increased by 4.6 times and 3.8 times compared with non-Hispanic white adults.
These results predict a significant increase in heat-related cardiovascular deaths in the United States by the middle of this century. Non-Hispanic black adults and older adults may be particularly affected. This increase is due to a combination of more days with a high heat index, an aging population, and population growth in warmer regions. These findings highlight the need for interventions to prevent heat-related diseases.
“The health burden of extreme heat will continue to increase in the coming decades,” Katana said. “This is also a health equity issue, as heatwaves have an unequal impact on different populations, potentially exacerbating health disparities that already exist.”
Funding: NIH’s National Heart, Lung, and Blood Institute (NHLBI). American Heart Association.
