A study published by the American Heart Association this week found that cardiovascular deaths from extreme heat could more than double by the middle of the century.
According to the study, researchers found that extreme heat was associated with 1,651 excess cardiovascular deaths per year between 2008 and 2019. By mid-century, the number of such deaths could as much as triple.
One reason for this involves the role of greenhouse gas emissions, researchers said.
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“Climate change and its many manifestations will play an increasingly important role on the health of communities around the world in the coming decades, ” said Dr. Sameed Khatana, lead author of the study and assistant professor of medicine at the University of Pennsylvania.
The study evaluated two hypothetical scenarios. One considered the successful implementation of currently proposed U.S. policies to reduce greenhouse gas emissions. In this scenario, researchers found that the number of cardiovascular deaths from extreme heat is projected to increase by 162% by the middle of the century.
Another scenario took into account if only minimal efforts were made to reduce emissions. In this projection, researchers found that the number of cardiovascular deaths from extreme heat has the potential to increase by 233% in the next 13-47 years.
In addition to greenhouse gas emissions, researchers also considered the future socioeconomic and demographic makeup of the U.S. population when estimating the possible impact of extreme heat on cardiovascular deaths between 2036 and 2065.
They found that adults aged 65 and older are expected to have a 2.9 to 3.5 times greater increase in cardiovascular death from extreme heat when compared to adults aged 20-64. This figure depends on how aggressively policies to reduce greenhouse gas emissions are implemented, the researchers noted.
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“In conjunction with the growth of more susceptible and vulnerable populations — aging adults and people relocating to warmer locations — heat-related cardiovascular disease deaths are expected to increase over the coming decades,” said Dr. Robert Brook, American Heart Association volunteer and professor of medicine and executive director of cardiovascular prevention at Wayne State University School of Medicine.
“Nevertheless, the study shows that the magnitude of adverse cardiovascular disease effects may be somewhat mitigated by taking earlier action to reduce greenhouse gas emissions that drive climate change,” Brooks added.
Along a similar note regarding the implementation of environmental policy, researchers also said that non-Hispanic black adults are expected to have a 3.8 to 4.6 times greater increase in cardiovascular death due to extreme heat, when compared to non-Hispanic white adults.
“Previous studies have suggested Black residents may have less access to air conditioning; less tree cover; and a higher degree of the ‘urban heat island effect’ — built-up areas having a greater increase in temperature than surrounding less-developed areas,” Khatana said.
Among adults in other racial or ethnic groups, the study did not find projected increases in deaths due to extreme heat. It also did not find projected increases between men and women.
The projections detailed in the study were based on county-by-county records from 2008-2019 for deaths that occurred during summer and had a primary cause of any cardiovascular condition, including heart attacks and strokes. They also included data, such as the age, sex, race and ethnicity of the deceased.
Additionally, they considered the number of days with a maximum heat index of 90 degrees or higher, or extreme heat days, during the month of a person’s death. According to researchers, the heat index takes into account heat and humidity, given how the human body responds in high temperatures and how high humidity interferes with the body’s ability to release heat by sweating.
Heat is the top weather-related killer in the U.S., taking an average of 164 lives annually from 1992-2021, according to NOAA. For context, the next deadliest weather-related killers, floods and tornadoes, kill an average of 88 and 71 people, respectively.
This year is on track to become Earth’s warmest year on record, according to the European Union’s Copernicus Climate Change Service. NOAA said El Niño is boosting the odds of a warmer-than-average winter in the northern tier of the U.S.