The findings are troubling when considering the 32 million Americans expected to become newly-insured under President Barack Obama's 2010 healthcare law.

But the results also suggest that the number of ER visits even out as a person remains either insured or uninsured for more than a year.

"Eventually, you'd suspect that their (ER) utilization would go down. So it could just be a short-term surge," said Dr. Adit Ginde, an emergency medicine doctor at the University of Colorado School of Medicine in Aurora.

Ginde and his colleagues analyzed data from about 160,000 adults who responded to a national health survey between 2004 and 2009.

Over 130,000 people -- about 83 percent -- were insured when they answered the survey. Of those, about 21 percent had visited an emergency room at least once in the past year, compared to 20 percent of the uninsured.

However, the researchers found differences when they grouped people by how long they had been insured or uninsured.

Of the 6,200 responders who'd had health insurance for less than a year, about 30 percent reported going to the ER recently, compared to roughly 20 percent of those who'd been insured more than a year.

The same was true for the uninsured people, the researchers reported in the Archives of Internal Medicine.

Out of close to 6,000 who'd recently lost their insurance, about 26 percent said they went to the ER in the past year, versus less than 19 percent of the continuously uninsured.

The link between losing or gaining insurance and ER trips remained even after the researchers took into account participants' economic status, race, general health and age.

Ginde's team also found that people with Medicaid, the U.S. health insurance program for the poor, were the most likely to visit the ER in the past year.

In another recent study, Ginde found that people on Medicaid have a harder time getting a prompt doctor's appointment, which may lead them to seek care at the ER (see Reuters Health story of March 27, 2012).

"Just because they have the insurance label doesn't mean they have a primary care doctor," he said, especially because Medicaid reimbursements are low and some doctors may shy away from taking on new patients in the program.

Regardless of their type of insurance, the newly-insured may have trouble getting an appointment to see a doctor, or they may have to wait a few days before there is an open time. The researchers say those types of barriers may make some turn to the ER.

Ginde told Reuters Health that the ER can be an attractive option for care.

"We're open 24/7 and we see everyone who walks through the door. We can do a large range of testing and treatment. It's certainly convenient in that way," he said.

As for the uninsured, Ginde said there could be a few reasons why they have an initial increase in ER use.

"There could be a (reason) why they lost their insurance. They may have gotten sick and lost their job... another possibly is that they are just used to getting care," he told Reuters Health.

Seeking help at the ER comes with a cost, even for the uninsured.

"When uninsured people use services, they do get billed for those services," Rachel Garfield, a senior researcher at the Kaiser Family Foundation in Washington, D.C., told Reuters Health.

According to Ginde, more primary care doctors and options for care may help curb the increases in ER use, but he said not to expect a drop in usage because of the 2010 healthcare law. Instead, he predicted "a slight uptick."

That uptick may cause problems for others seeking care in the ER too.

In the same journal issue, Dr. Mitchell Katz, from the Los Angeles County Department of Health Services, wrote: "When (emergency departments) are crowded, patients who have serious problems are at risk for delayed treatment."

SOURCE: bit.ly/GYL1wy and bit.ly/GYLtuJ Archives of Internal Medicine, online March 26, 2012.

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