Within the past five years,Chainkeen Dr. Sameed Khatana says, many of his patients in Philadelphia have realized how climate change hurts them, as they fared poorly with each wave of record heat.

"Like most public health issues in the United States, extreme heat is also a health equity issue," says Khatana, who is a cardiologist at the University of Pennsylvania and the Veterans Affairs hospital in Philadelphia.

Record heat scorching the country is especially dangerous for the many, many people with common conditions like diabetes, obesity and heart disease. And within cities, many vulnerable communities face greater exposure to heat, fewer resources to address it or escape it, and higher rates of the diseases that make heat more dangerous for people.

Risk piled upon risk

Khatana, who also has a master's in public health, is well acquainted with how these risk factors overlap.

"There's some evidence that the greatest proportion of deaths that occur related to extreme heat are likely due to cardiovascular conditions," says Khatana.

Heat stroke happens when the body's core temperature rises so fast and high it rapidly becomes lethal. The heart pumps blood away from vital organs to dissipate heat. That can overload weakened hearts or lungs. Many of his patients also have obesity or diabetes, which can affect circulation and nerve function. That also affects the ability to adapt to heat.

In addition, common medications his patients take for heart disease — beta blockers and diuretics — can make heat symptoms worse.

"Now, this isn't to say that people shouldn't be taking those medications," Khatana cautions. "It is just to highlight the fact that some of the medications that are necessary for people with heart disease can also impair the body's response to heat exposure."

Just as seen in other public health concerns like obesity or COVID-19, the elderly, communities of color, and people with lower socioeconomic status bear the highest risk. Those most in danger live in the Deep South and across the Midwest — where heat, older populations and rates of complicating disease run highest.

This is the same area that's been dubbed "the stroke belt," Khatana notes, and he says he fears the public measures to fight heat won't reach the people most at risk.

"It's a little bit disorganized for many places. It's unclear how people are going to get to these cooling centers. Is there appropriate public transportation?" Khatana says. "How are people going to be made aware where these centers are? Is someone going to reach out to people who, perhaps, are physically impaired?"

A business incentive for change?

Steven Woolf, director emeritus at the Center for Society and Health at Virginia Commonwealth University, notes historically marginalized communities often have fewer trees and public parks. That means temperatures can run 15 to 20 degrees hotter in those areas, compared to leafier areas a few miles away.

"Planting trees and creating areas of shade so that people have a way of protecting themselves in extreme heat" is important, Woolf says. He also notes changes in roofing materials to make them reflect rather than absorb heat could help in communities where air conditioning can also be more scarce.

Woolf says such changes could be implemented in two to three years time, if there's a push to find the money to invest in it. And since heat affects workers and productivity, Woolf hopes businesses will lead.

"Eventually, I suspect businesses and employers will do the math and see that the payoff in terms of lost productivity more than outweighs the upfront expenses of retooling their infrastructure to deal with extreme heat," he says.

As more parts of the country come face to face with the health and safety costs of extreme heat, he says he hopes there will also be more political will to back these changes.