A tenet of President Obama's health reforms — that insuring more Americans will reduce reliance on expensive hospital emergency rooms — is getting undercut by studies that reveal a more complicated relationship between insurance status and ER use.

Opponents of the Affordable Care Act leapt on a study published in January by the journal Science, showing that more Oregonians sought ER care after receiving coverage under an expansion of that state's Medicaid program five years ago.

This defied the logic embraced by many, including the president, that insurance connects people with primary care doctors and gives them the preventive care to avoid health crises that require emergency care.

Now comes a study from the University of Minnesota that has gained less attention, but has similar implications.

A research team led by the U's Nathan Shippee found that in a sample of Minnesotans covered by state-subsidized health programs, simply having access to affordable coverage wasn't a predictor of ER usage.

What made a difference was the number of nonfinancial barriers to medical care, such as a lack of transportation to clinics or of affordable child-care so parents could go see doctors. Patients facing such barriers ended up in the ER more frequently — presumably because nonfinancial barriers prevented them from seeking primary care, even if they had insurance to pay for it.

"Coverage and access aren't the same thing," Shippee said.

This doesn't mean that the expansion of health insurance under the Affordable Care Act is a bad idea. Balancing the argument are numerous studies showing health benefits from providing insurance to those who don't have it, and of providing better insurance to people with shell policies that pay benefits only in dire emergencies.

But will expanded coverage efficiently cut ER usage? Shippee said that might require more community services to address the nonfinancial barriers that keep people from seeing their own doctors.