It was only a few months ago that we were all experiencing the extreme heat of summer 2023. Well, we made it through, but extreme heat can have a major impact on a person’s heart. A new report says over the next few decades these effects of this increasing heat may prove more deadly, especially to Black adults, seniors and people living in urban areas, who are at greatest risk.
The heat index, which includes temperature and humidity, was at least 90 degrees on an average of 54 days each summer between 2008-2019 and were associated with almost 1700 excess heart-related deaths each year.
According to the study, without a major push to reduce fossil-fuel use and development across the world as a way to reduce planet-warming, the number of days on average at 90 degrees and above could reach 80 days and account for 5,500 excess heart-related deaths per year.
If fossil-fuel development continues to expand globally and the world only makes minimal efforts to reduce planet-warming pollution, there could be 80 days of extreme heat each summer and the number of heat-related cardiovascular deaths in the U.S. could more than triple – to about 5,500 excess deaths per year, the researchers found.
If planned and ongoing climate change mitigation measures are put into place, the result could lead to a jump to 71 days of extreme heat per year and more than 4,300 excess cardiovascular deaths related to excess heat by the middle of the century.
Heart disease is the leading cause of death in the U.S. overall and extreme heat causes a small share of total cardiovascular deaths in the U.S. — about 1 in 500 right now, said Dr. Lawrence Fine, a senior adviser at the National Institutes of Health’s National Heart, Lung, and Blood Institute, which partially funded the new research.
“The thing about heat-related deaths is that they’re concentrated to when it’s very hot, and they’re also concentrated in people who are at greater risk because of their health conditions or other conditions,” he said.
“It’s important to address the root causes of the increase in temperature and heart disease, but we also want people to know if they’re vulnerable and to have a specific plan for what to do when they find themselves in a very hot environment.”
The heart is particularly susceptible to the effects of heat.
The human body can only operate within a narrow temperature range, and the heart plays a critical role in keeping the system regulated, said Dr. Sameed Khatana, an assistant professor of cardiovascular medicine at Penn Medicine and senior author of the new study. When the heart has to work harder than it’s used to, the consequences can be deadly for some.
“When the body senses that its temperature is going up, various things start kicking into gear. A key component of that is that the heart beats faster and harder to get blood away from the core of the body, to transport heat away from the vital organs,” he said. “For people with pre-existing cardiovascular diseases, their heart might not be able to keep up with the increased demands on the cardiovascular system that temperature is causing.”
Longer exposures to heat can also lead to more complex changes such as increased inflammation and blood clotting that can raise the risk for heart attack and stroke, he said.
Black adults are particularly vulnerable to the heart-related harms of extreme heat. Over the next few decades, heat-related cardiovascular deaths could grow six-fold among Black adults in the U.S., according to the scenarios analyzed in the study – compared with a projected 2.4 times increase among White adults in the worst-case scenario.
Seniors age 65 and older and adults living in metropolitan areas are also projected to be disproportionately affected. Demographic shifts in the U.S. – such as an aging population, diversification and growth in cities – could exacerbate baseline vulnerabilities.
“In some ways, you could argue that no one should be dying due to heat exposure. There is a simple solution: you just get someone to a cool environment,” Khatana said. “But like most public health issues in the United States, the health impacts of climate change – and extreme heat, specifically – are also health equity issues.”
People who are vulnerable to heat exposure are likely vulnerable in many other aspects of their lives – perhaps living in areas with less tree cover or without access to air conditioning. Black people are also more likely to live with conditions that put their heart health at risk, including higher rates of hypertension and diabetes.
“Solutions need to be targeted at people who are the most vulnerable,” Khatana said. “If mitigation efforts are not taken, if efforts to reduce emissions aren’t made, then these inequities that we’ve already seen might continue to widen.”