Unhoused people are far more likely to get sick in the heat. Now there’s data to prove the risk

Visits to the emergency room spike when it gets really hot, according to public health data. But for many years one of the populations most affected by extreme heat — the unhoused — have been left out of that data.

Now, we know this: Californians experiencing homelessness are 38% more likely to visit the emergency room because of extreme heat, despite accounting for less than half a percentage point of the total population.

That’s according to a new analysis by Tracking California, a program that collects and analyzes data on health hazards across the state.

“We always knew that unhoused individuals were at much higher risk on extreme heat days, and now there is that empirical evidence,” said Shubhayu Saha, executive director of Tracking California.

Their report found that unhoused people were also 11% more likely to visit the hospital for heart and respiratory illness on high heat days, which may reflect how heat can exacerbate preexisting conditions like heart disease, or coincide with air pollution like smog that gets worse during hot days, Saha said.

The solutions, however, are not simple and require addressing entrenched societal problems — a lack of affordable housing, high electricity bills that can force people to keep their A/C off even if they have it, and unequal access to shade and green space outdoors.

Addressing the acute need

Meanwhile, local shelters and doctors have been responding to acute needs.

In the San Bernardino Valley, Dr. Rodney Borger has recently treated unhoused patients for burns, from laying on hot pavement, and severe dehydration.

On Skid Row in L.A., UCLA physician Mary Marfisee has treated more and more patients with severe dehydration, heat rashes and heat exhaustion. Among the chronically unhoused, she said, addiction and mental health issues can also interact with heat in dangerous ways.

Dr. Mary Marfisee conducts a brief breathing check on a woman on Los Angeles' Skid Row last year.

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Zaydee Sanchez

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For NPR

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“The medications for mental illness can affect the hypothalamus, and that's your set point for temperature regulation,” Marfisee said. “Mental illness itself can lead to those temperature regulation difficulties, so they think they're cold, when they're really not.”

Yolanda Breland,  the senior director of community engagement at the Los Angeles Mission, has noticed the increase in homelessness, and more challenges related to the heat.

“ It's too hot for them to be in their tents or under any type of shelter because that just retains the heat,” she said.

Breland also said this week they’ve seen a big increase in people coming to the mission’s lobby and courtyard, where they can access air conditioning, cold water, showers, misters and shade.

ER visits for heat in general on the rise

It’s not just the unhoused — people with housing account for the vast majority of heat-related visits to the ER.

According to publicly available data, emergency room visits have been steadily rising with the heat in July and August across much of Southern California.

In L.A. County, most of the cases involve adults over 65 and people in the hottest areas, said Dr. Nichole Quick,  chief science officer at the county’s Public Health Department.

In Riverside County, meanwhile, the most affected group showing up in the data are men between 18 and 44.

“In the Coachella Valley especially, we have large farm worker populations,” said Dr. Shunling Tsang, the county’s deputy public health officer.

Emergency room visits have been steadily rising during the hotter months, according to L.A. County's public health data dashboard.

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Courtesy L.A. County Department of Public Health

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Having more detailed data can help improve public health responses, since every community is different, said Dr. David Eisenman, who developed ZIP code level data of excess ER visits due to heat from 2008 to 2018.

And as human-caused climate change drives up average temperatures and worsens heat waves, that work will only become more urgent.

In Riverside County, middle-aged men in the Coachella Valley are most impacted by heat illness, likely reflecting the experience of farmworkers.

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Courtesy Riverside University Health System

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“That way city officials, public health departments, emergency planners, also parks and recreation people can make informed decisions about where they want to prioritize putting their resources,” he said.

Still, such data remains limited — community health centers and other clinics that primarily serve low-income households are not part of that public health data, Saha said.

“Just being able to track what is happening in a range of different health facilities,” he said, “would really give us a much better picture of who is at risk and what we can do for them.”