The promise of cheaper housing brought Shari Castaneda to Palmdale, Calif., in northern Los Angeles County, about nine years ago.

The single mom with five kids had been struggling to pay the bills. “I kept hearing that the rent was a lot cheaper out here, so I moved,” she said.

But when she developed health problems — losing her balance and falling — Castaneda found fewer care options in her new town. Unable to find local specialty care, she traveled nearly 65 miles to a public hospital in Los Angeles, where doctors discovered a tumor on her spine.

Then she had to drive nearly 75 miles to the City of Hope cancer center in Duarte, Calif., for an operation to remove the growth. The procedure left her partially paralyzed. “I walked into the hospital and I never really walked again.”

Castaneda, 58, receives Social Security disability payments and is enrolled in Medi-Cal, the state’s Medicaid program for low-income people. “There are no doctors available here,” said Castaneda. “I called every single one of them in the book, and nobody takes Medi-Cal out here.” Instead, Castaneda now sees doctors nearly 50 miles away in Northridge.

Suburbs in the United States, often perceived as enclaves of the affluent, are home to nearly 17 million Americans who live in poverty — more than in cities or rural areas — and growing demand for care strains the capacity of suburban health services to provide for them, according to a recent study in Health Affairs. Suburban areas have historically received a fraction of health funding that cities have, leaving them with inadequate infrastructure and forcing people like Castaneda to scramble for the medical attention they need.

The Health Affairs study found that about a fifth of the suburban poor are uninsured, and many who do have health insurance — especially people on Medi-Cal — either can’t find providers or must travel far for appointments.

The Affordable Care Act cut California’s uninsured rate from 17 percent in 2013 to about 7 percent last year due largely to the Medicaid expansion, which added more than 3.7 million adults to the state’s Medi-Cal rolls. But that has not ensured access to health care for millions of suburbanites, said Alina Schnake-Mahl, a doctoral candidate at the Harvard T.H. Chan School of Public Health in Boston, who was lead author of the Health Affairs study.

“That really goes against the idea that everyone in the suburbs is insured because everyone has a white-collar job with coverage,” she said.

Coverage doesn’t equate to care even for patients with Medi-Cal, as Castaneda can attest. Before the health law, they had trouble finding doctors who would see them because of Medi-Cal’s low payment rates. That problem intensified as millions more signed up for Medi-Cal, driving many enrollees to seek services at safety-net care facilities.

Health care services in the suburbs “are not robust enough to fill the needs” of a growing low-income population, said Charlie Gillig, supervising attorney at the Health Consumer Center of Neighborhood Legal Services of Los Angeles County, which has advised Castaneda about medical transportation services under Medi-Cal.

One-half of California’s 39 million residents live in suburbs, and rates of poverty among them range from nearly 25 percent around Bakersfield, in the Central Valley, to about 8 percent in the suburbs outside San Francisco, according to an analysis by Elizabeth Kneebone, research director at University of California-Berkeley’s Terner Center for Housing Innovation and a senior fellow at the Brookings Institution. The same analysis showed that 2.7 million suburban Californians lived below the poverty line in 2016, compared with 1.9 million in major cities.

Castaneda, who uses an oversized power wheelchair, says it’s difficult — “often impossible” — to arrange for a ride in a van. Getting to the doctor has become a long, painful ordeal.

And that’s if she can even schedule a visit, said Castaneda, noting that she also faces long wait times for her doctor in Northridge, a suburb that has seen an influx of patients from poorer areas. “You can’t get an appointment when you’re sick … so I’ve just been waiting and waiting,” she said. “They told me, ‘If you get sick enough, just go to the emergency room.’”

Of course, it can also be tough to get a clinic appointment or see a specialist in cities, but in the suburbs, Gillig said, “geography exacerbates an already existing problem.”

In his recent book on the changing geography of poverty, Scott Allard, a professor of public policy and governance at the University of Washington, showed that funding for human services was as much as eight times higher in urban areas than in the suburbs.

California’s metropolitan areas have had many decades to build up massive health care systems to serve the poor, including county hospitals, federally qualified health centers and community clinics. But the current scale of suburban poverty is a recent development.

Policymakers struggle to serve the health needs of cities in eastern Contra Costa County, about 50 miles from San Francisco. In Oakley, for example, business and community leaders lobbied hard for a new health center, which opened in 2011.

“There’s a huge need out here, especially for people who are undocumented or uninsured. They don’t have anywhere else to go,” said Leticia Cazares, regional manager for La Clinica, which operates the new health center. The clinic has two doctors and a nurse practitioner to serve 3,000 patients, most of whom are on Medi-Cal.

Many of the people who visit community clinics like the one in Oakley lack insurance, either because they are undocumented immigrants or because they make too much money to qualify for Medi-Cal — or subsidized coverage under Obamacare — and can’t afford it on their own.

Alex G.’s family fits both scenarios. Her husband, Edward, and 8-year-old son — also named Alex — are U.S. citizens, but she is an undocumented immigrant. The family lives in Brentwood, a town of about 60,000 in eastern Contra Costa County.

A 32-year-old community college student who declined to give her last name for fear of deportation, Alex has applied for permanent residency — a long process with an uncertain outcome.

Her husband has “a good job” as a programmer of industrial machines. He has employer-based insurance, but it covers only him. For Alex and her son to be covered, the family would have to pay $1,200 a month. Given California’s high cost of living, “we just can’t afford to pay that,” Alex said. Her husband’s salary of $70,000 is too high for Medi-Cal or Obamacare subsidies.

Alex recently experienced sharp stomach pains and had to wait several days for a mobile clinic that parks in front of a nearby community center once a week.

Whenever her son has an ear infection or a fever, Alex takes him to the free mobile clinic. “Not having insurance, I worry all the time about him getting sick,” she said.

Kaiser Health News (KHN) is a national health policy news service. It is an editorially independent program of the Henry J. Kaiser Family Foundation which is not affiliated with Kaiser Permanente.