They tend to have less access to primary care doctors than the privately insured, researchers say.

(HealthDay) -- Medicaid patients have more difficulty getting primary care and visit hospital emergency departments more often than those with private insurance, a new study finds.

An analysis of data from more than 230,000 adults who took part in the U.S. National between 1999 and 2009 showed that about 16 percent of had one or more barriers to primary care, compared to 9 percent of people with .

Barriers to care included not being able to reach a doctor by phone, not being able to get a timely appointment with a doctor, and lack of transportation to the doctor's office.

The researchers also found that nearly 40 percent of visited a during the previous year, compared with 18 percent of patients with private insurance.

When the researchers looked at all patients with barriers to primary care, they found that Medicaid patients still were more likely to visit the emergency department than those with private insurance.

Among patients with two or more barriers to primary care, 61 percent of Medicaid patients and 29 percent of privately insured patients visited a hospital emergency department during the previous year.

The study was published online in the .

"Even those Medicaid patients who have -- and that is less likely than for people with private insurance -- report significant barriers to seeing their doctor," senior study author Dr. Adit Ginde, of the University of Colorado School of Medicine, said in a journal news release.

"Medicaid patients tend to visit the ER more, partly because they tend to be in poorer health overall," Ginde added. "But they also visit the ER more because they can't see their primary care provider in a timely fashion or at all."

"The efforts by some states to keep Medicaid patients out of the ER do not take this lack of access to primary care into account," Dr. David Seaberg, president of the American College of Emergency Physicians, said in the news release. "It puts both patients and providers into an impossible position that will only get worse as more people enroll in Medicaid."

More information: The U.S. National Library of Medicine explains how to choose a primary care provider.