(CNN) Half of American adults have at least one chronic medical condition, such as type 2 diabetes or skin cancer. Among chronically ill patients ages 18 to 64, health coverage increased by nearly 5% in the first year that affordable insurance options were made available through Obamacare, according to a new study published Monday in the journal Annals of Internal Medicine.

"We wanted to see how many people were uninsured and clearly needed health insurance," said Dr. Hugo Torres, lead author of the study and a practicing internist with Cambridge Health Alliance in Cambridge, Massachusetts.

Torres and his colleagues focused on chronically ill patients, "the population that needs coverage the most, it could be argued," said Dr. Danny McCormick, senior author of the study and associate professor at Harvard Medical School.

"We know the prevalence of chronic diseases is going up, and about half of Americans have a chronic disease, and when I'm saying 'chronic disease,' we're talking about things like cancer, heart disease, arthritis, asthma, diabetes," he said.

It is well-known that these conditions are the leading cause of death and disability in the United States but also that most of these conditions can be controlled with the right medication and good access to medical care.

The research team focused on adults between the ages of 18 and 64, since this age group was the target population of the Affordable Care Act. Younger people have traditionally been considered dependents, able to be covered by their parents' plans, while those 65 or older usually have access to Medicare.

For data, Torres, McCormick and their colleagues turned to the Behavioral Risk Factor Surveillance System. Established in 1984, this telephone survey collects data from US residents living in all 50 states, the District of Columbia and three US territories. All told, the research team analyzed survey information provided by 606,277 adults between the ages of 18 and 64 who had a chronic disease.

Increased coverage

During 2014, the first year Obamacare health exchanges went into effect, insurance coverage increased by 4.9% among the chronically ill, and 2.7% more had a checkup, the study found. However, the ACA had no impact on the number of chronically ill people with a personal physician.

On the flipside, 14.9% of chronically ill patients continued to lack insurance, 27.6% did not have a checkup, 22.8% did not visit a physician, and 18.1% lacked a personal physician one year after the implementation of Obamacare, the researchers found. In 2013, nearly one in five (PDF) chronically ill patients -- about 15.7 million people -- lacked health insurance, Torres said.

Increases in medical care coverage after Obamacare varied by state. Coverage increased more in the states that expanded Medicaid than in states that did not, pointed out McCormick.

"The absolute percentage point difference was not very big," McCormick noted, explaining that in Medicaid expansion states, about 5.7% of the chronic disease population got new insurance, compared with 4.2% in non-expansion states. "So that's about 1.5% absolute difference, but the relative difference is 35%."

One caveat, McCormick said, is that the study focused only on the first year of Obamacare.

"Estimates put forth by the Department of Health and Human Services show that there were additional gains (in health coverage) of about 2 percentage points through the first quarter of 2016," Torres said.

Disparities in coverage

Although racial and ethnic minorities saw improvements during the ACA's first year, approximately one in five black people and one in three Hispanic people with a chronic disease continued to lack coverage and access to care, according to the study results. Among blacks, 17.5% continued to lack coverage, while 26.8% did not visit a doctor. Among Hispanics, these figures were 29.7% and 32.9%.

What kept the chronically ill from seeking care?

"The immigration issue is important, particularly in the Hispanic community," Torres said. "There are several barriers to immigrants getting care, including waiting periods for legal immigrants to obtain Medicaid and the banning of undocumented immigrants from obtaining insurance on the health exchanges."

Another problem faced by some patients was a lack of available doctors, McCormick said, adding that this is not something he and his co-authors studied, though previous research has addressed the issue.

"There was an expansion of coverage, so a large number of people became newly eligible for getting insurance got insurance, but there wasn't any equivalent mechanism to increase the number of primary care doctors available to actually see those patients," he said.

Another hurdle chronically ill patients must overcome is the high cost of medical care, including copayments, deductibles and other out-of-pocket expenses. Generally, out-of-pocket costs were higher in the Obamacare-purchased plans compared with employer-sponsored plans, the researchers said.

In light of promises to "repeal and replace," there are questions "we have to ask as a society," noted Torres. "Do we want to restructure health care to avoid unnecessary suffering by millions of (mostly poor) people with chronic diseases and no health insurance?"

Beyond Obamacare

"The study confuses coverage with care," said Dr. Jane Orient , an internal medicine doctor and executive director of the Association of American Physicians and Surgeons, a nonpartisan professional association. "I think it sheds no light whatsoever on whether people with chronic diseases are feeling better, living longer or having fewer complications."

Orient, who did not participate in the research, added that it would be impossible to be able to track these effects in just one year, in any event. "The insurance effect on treatment would be very indirect."

But Dr. Ken Thorpe, chairman of the Partnership to Fight Chronic Disease (PDF), liked the simple focus of the study.

"If we're ever going to do anything about health care spending, we've got to find ways to prevent the growth in chronically ill patients and do a better job of keeping these patients healthy," said Thorpe, who did not participate in the research.

"If you look at the data, about 86% of what we spend on health care is linked to these chronically ill patients," said Thorpe, a former White House health policy adviser under President Clinton. Thorpe added that the US spends about $3 trillion (PDF) on health care.

"When I think about health reform that we're going to be discussing pretty soon, that's, to me, the core of it: It's really to build a prevention system and to build a system that's much better and nimble in managing these patients with multiple chronic health care conditions," he said.

Routine access to good primary care and medications is critically important because it keeps chronically ill patients out of hospitals and emergency rooms, which are more expensive than routine care, according to Thorpe.

Uninsured people under age 65 averaged $1,627 in ER expenses in 2013, according to the Medical Expenditure Panel Survey conducted by the Agency for Healthcare Research and Quality.

Dr. Mary Applegate , associate dean of the School of Public Health at the University at Albany, estimates the price of a single ER visit at about $1,000 and a doctor's office visit at about $100 without insurance. The higher price is "because you're paying for all the infrastructure that's there just in case you need to have your heart restarted or you need to have emergency surgery," said Applegate, who did not participate in the study.

So going to an ER for something relatively minor, which an uninsured chronically ill person may end up doing, "is a lot more expensive, and it takes space and personnel away from the real life-threatening kinds of emergencies that need to be taken care of in the ER, people like car crash victims or people having a heart attack or a stroke," she said.

Overall, Applegate thought the study was "well-done," adding that some of the underlying problems associated with health care access have been issues for decades, such as the shortage of community doctors available to provide primary care.

"I went to medical school in the early 1980s, and a study came out then that decried the over-specialization of medicine in this country and talked about how we should have many fewer specialist and many, many more primary care physicians," Applegate said.

She suspects this trend may have gotten worse due to the much higher cost of medical school, often paid for by student loans. Primary care physicians "get paid way less than specialists," she said.

Another underlying problem that was around long before Obamacare became a hotly contested topic is the number of non-financial barriers to optimal medical care for some people, including chronically ill patients.

"You give somebody a health insurance card; that gives them a way to pay for health care," she said, but there may be other barriers to access, including a lack of transportation, language barriers, getting paid time off, and living in a neighborhood where there's access to healthy food and the ability to walk safely. Consider too that people with chronic illnesses may have disabilities, added Applegate, such as amputations or difficulty climbing stairs.

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When it comes to staying healthy, all of us, including the chronically ill, "have a lot to do ourselves, not just show up at the doctor's office," she said. "And most of it is fairly straightforward stuff. It's going out for a walk. It's eating healthy foods. It's having social interactio,n because isolation is another huge factor that increases health problems." It's everything your grandmother would tell you, she said.

"Passing the Affordable Care Act, I think a lot of people felt like that was just the magic wand and the world would be healthy all of a sudden," Applegate said. "It's a step in the right direction but not the whole thing."