TUESDAY, Aug. 10 (HealthDay News) -- Increasing numbers of Americans, especially adults on Medicaid, are using hospital emergency rooms for their health care, say researchers from the University of California, San Francisco.

Using data from 1997 through 2007, the researchers found that ERs are increasingly serving as "safety nets" in American health care, because by law they must treat all patients regardless of insurance or their ability to pay, the researchers say.

"There are alarming trends in emergency department visits," said lead researcher Dr. Ning Tang, an assistant clinical professor of medicine at the university.

"In 1999 adults with Medicaid visited the emergency department at a rate 3.5 times higher than the rate of adults with private insurance, and in 2007 adults with Medicaid visited the emergency department at a rate five times that of adults with private insurance," she said.

Many of these visits by Medicaid patients were for conditions that could have been managed in a primary care clinic, Tang noted.

The report is published in the Aug.11 issue of the Journal of the American Medical Association.

To calculate how emergency departments were being used, Tang's team reviewed data from the National Hospital Ambulatory Medical Care Survey.

The researchers classified emergency departments as "safety-net facilities" if more than 30 percent of all visitors were on Medicaid; if more than 30 percent of visits were by people without health insurance; or if more than 40 percent of visits were by Medicaid and uninsured patients.

The number of emergency departments designated as "safety net" centers increased from 1,770 in 2000 to 2,489 in 2007, the researchers found.

They found that during the time period studied, annual emergency department visits went from about 94.9 million to 116.8 million, an increase of 23 percent, which is almost twice what was expected based on population growth, they said.

The biggest increase in ER visits was seen in people 18 to 44 years old and those 45 to 64.

But there could soon be a problem with demand and supply: At the same time that ER visits mushroomed, the number of emergency departments fell by 5 percent, the researchers noted.

Moreover, visits among people receiving Medicaid went from about 694 visits per 1,000 people to about 947 visits per 1,000 people, while visits by adults with private insurance, no insurance or Medicare remained stable, they found.

Because of increased volume, median wait time for treatment increased from 22 to 33 minutes during the study period.

Strategies are needed to prevent further stressing of this "safety-net" system, the authors added.

The findings suggest that access to primary care is a key problem, Tang said. "Whether it's primary care physicians are not accepting new patients with Medicaid or that there aren't enough primary care physicians, we need to dig a little bit deeper," she said.

Whether health care reform will help isn't clear, Tang said. With more people on Medicaid, the future is uncertain, she said. Even increasing reimbursement for doctors may not solve the problem, she added.

Tang's group also noted that the recession may make the problem even worse. "One of the nation's most severe recessions started in 2008, and with record job losses in 2008 and 2009, an estimated additional 5.8 million Americans became uninsured and an estimated 5.4 million enrolled in Medicaid and SCHIP [State Children's Health Insurance Program]," they write.

Dr. Tamara R. Kuittinen, director of medical education in the department of emergency medicine at Lenox Hill Hospital in New York City, wasn't surprised by the findings. "It's what we experience on a day-to-day basis," she said.

There is no single explanation for the increase in emergency room visits, but rather a combination of factors, Kuittinen said. Hospitals and emergency departments are closing around the country, so naturally there is an increase in people using the remaining emergency rooms, she noted.

More individuals are receiving Medicaid assistance, she said, and many primary care doctors aren't taking on new Medicaid patients because of low reimbursement. "It's a problem with the system," she said.

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