In his cardiology practice in Philadelphia, Sameed Khatana, MD, MPH, feels the effect of extreme heat. During the hottest summer days, more patients describe “difficulty breathing and their heart racing,” he said. When a heat wave struck the Pacific northwest in 2021, killing over 600 people, he knew that extreme heat “would be a public health issue that clinicians and public health officials need to pay attention to.”

Khatana decided to look further into this issue, along with LDI Senior Fellows Lauren A. Eberly, Ashwin S. Nathan, and Peter W. Groeneveld. The group projected the number of excess deaths linked to climate change from 2036 to 2065. Their study, published in Circulation, estimated that by midcentury the amount of heat-related cardiovascular deaths in the U.S. would rise by up to 233%, as climate change raises the intensity, frequency, and duration of extreme heat.

They found an estimated 1,600 excess deaths occurred annually from 2008 to 2019 associated with extreme heat. That death count is expected to more than double by midcentury if greenhouse gas emissions rise moderately, and more than triple if those pollutants rise to a greater degree.

This burden is not shared equally among the population. Patients who are older and Black will experience more of the health effects from extreme heat. 

As a result, “climate change and extreme heat are public health and health equity issues,” said Khatana, LDI Senior Fellow, Assistant Professor of Medicine in the Division of Cardiovascular Medicine at the Perelman School of Medicine, and a physician at the Philadelphia Veterans Affairs Medical Center

Figure 1: Estimated number of excess cardiovascular deaths associated with extreme heat per 1 million adult residents in the current (2008–2019) and midcentury (2036–2065) periods in the contiguous United States.

Extreme Heat and the Cardiovascular System

Extreme heat, which refers to temperatures and humidity far higher than usual for a particular area, can affect the heart and blood vessels’ function. “The cardiovascular system is a key component of the temperature regulation system in the body,” says Khatana. People with pre-existing cardiovascular conditions or risk factors are at a higher risk for effects linked to extreme heat exposure, according to Khatana. These adverse health effects may include increased heart rate, dehydration, heart attacks, and stroke.

Underlying Disparities Exasperated

Older adults and non-Hispanic Black individuals in the U.S. often find themselves at risk of facing adverse health effects due to extreme heat. In 2018, Black Americans were 30% more likely to die from heart disease than white Americans. They also develop heart disease at a younger age. 
This increased risk is due, in part, to historic underinvestment and a continued lack of infrastructure in marginalized communities. Residents in these areas often lack access to air conditioning and suffer from the urban heat island effect, where streets become excessively hot. As a result, the study authors say that residents in these areas are among the most vulnerable to the health impacts of climate change.

Focusing on Mitigation Across All Levels of Government

Climate change is a public health emergency that requires attention from the local, state, and national government. The authors point to several mitigation strategies that can make a significant impact on those most vulnerable to extreme heat, including: 

As the number of heat waves and extreme weather events continue to rise, the relationship between climate and cardiovascular health “requires a coordinated effort on several levels, both at the health system as well as local, state, federal, and global policy levels,” says Khatana.

The study, “Projected Change in the Burden of Excess Cardiovascular Deaths Associated With Extreme Heat by Midcentury (2036–2065) in the Contiguous United States,” was published on October 30, 2023 in Circulation. Authors include Sameed Ahmed M. KhatanaLauren A. EberlyAshwin S. Nathan, and Peter W. Groeneveld.


Mackenzie Bolas

Policy Coordinator

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