Heat-related cardiovascular deaths may double in the coming decades

A new study published in the journal Circulation has found that cardiovascular fatalities attributed to extreme heat in the United States are on a trajectory to potentially more than double by the mid-21st century. 

“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 lead author Sameed Khatana, an assistant professor of Medicine at the University of Pennsylvania and a staff cardiologist at the Philadelphia Veterans Affairs Medical Center. 

“Climate change is also a health equity issue as it will impact certain individuals and populations to a disproportionate degree and may exacerbate preexisting health disparities in the U.S.”

Focus of the study 

By employing county-level data from 2008-2017, the experts established a correlation between increased extreme heat days and cardiovascular deaths. 

This analysis set the stage for projections into the future, incorporating anticipated demographic changes and greenhouse gas emissions scenarios. 

What the researchers learned 

The investigations revealed a 162 percent increase in excess cardiovascular deaths due to extreme heat by 2036-2065, even if proposed emissions reductions are achieved. Without these reductions, the increase could reach 233 percent.

The key findings of the study include:

• From 2008 to 2019, extreme heat was linked to an average of 1,651 additional cardiovascular deaths annually.
• A projected 162 percent increase in excess cardiovascular deaths due to extreme heat is expected by mid-century, even with proposed greenhouse gas emissions reductions.
• If greenhouse gas emissions reductions are not implemented, the increase in excess cardiovascular deaths could reach 233 percent.
• Adults aged 65 and older may face a 2.9 to 3.5 times greater increase in heat-related cardiovascular deaths compared to adults aged 20-64.
• Non-Hispanic Black adults are projected to experience a 3.8 to 4.6 times greater increase in cardiovascular deaths due to extreme heat compared to non-Hispanic white adults.
• Projected increases in deaths due to extreme heat were not significantly different among adults in other racial or ethnic groups, or between men and women.

Multifaceted issue

“The magnitude of the percent increase was surprising. This increase accounts for not only the known association between cardiovascular deaths and extreme heat, but it is also impacted by the population getting older and the proportionate increases in the number of people from other races and/or ethnicities in the U.S.,” Khatana explained, highlighting the multifaceted nature of the issue.

Study co-author Robert Brook from Wayne State University School of Medicine echoed these concerns and emphasized the urgent need for action. “Even under the more optimistic moderate scenario of this study, greenhouse gas emissions will increase for some time before tapering down. Moreover, most of the pollutants persist in the atmosphere for numerous years, and as such, the long-term trend is for significant increases in the frequency of extreme heat events despite near-term actions.”

“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. 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.”

Underestimated projections 

As Brook further explained, although such projections are alarming, they are most likely underestimations of what may actually happen. “The projections of this study focus on cardiovascular disease deaths, and, therefore, they represent conservative estimations of the adverse effects on cardiovascular health due to extreme heat,” he said. 

“Nonfatal heart attacks, strokes, and heart failure hospitalizations outnumber fatal events and are also highly likely to be linked with extreme heat days. The full extent of the public health threat, even just due to cardiovascular death, is likely much greater than presented in this study. “

The forecasts bring to light the potential of infrastructural changes, like enhancing greenery in communities, to mitigate the impact of extreme heat on individuals in the U.S. While certain European studies provide some evidence supporting this approach, there is a noticeable gap in similar research within the United States.

Finally, Brook also stressed the role of pollution linked to extreme heat. “Fine particulate matter air pollution (PM2.5) causes more than 6 million deaths per year. This study adds to the evidence that the full extent of the harmful effects posed by air pollutants extends beyond PM2.5. By substantially increasing extreme heat days, greenhouse air pollutants pose yet further threats to our well-being,” he concluded.

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