Fewer patients with employer-sponsored insurance are visiting their primary care doctors, but more are seeing other advanced practice providers (APPs), according to a new study.

The Health Care Cost Institute (HCCI) dove into claims data from Aetna, Humana, UnitedHealthcare and Kaiser Permanente from between 2012 and 2016 and found an 18% decrease in office visits to primary care physicians.

However, in that same window, visits to all other providers increased by 14%. In particular, visits to nurse practitioners and physician assistants increased by 129% over those four years.

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Convenience could be playing a role in this, John Hargraves, a senior researcher at HCCI and one of the report’s authors, told FierceHealthcare. For example, if a patient calls their local primary care office and is given a significant wait to see their doctor but can see a nurse practitioner or physician assistant sooner, many will choose the latter.

“A lot of patients are not so biased toward seeing a doctor that they’re going to wait,” Hargraves said. “They aren’t that concerned when they show up at the office and at the office is a nurse practitioner.”

Nurse practitioners, physician assistants and other advanced practice clinicians, however, can play a key role in addressing care access gaps—particularly in rural areas, research suggests. They are especially valuable as the physician shortage grows, and the number of APPs is expected to eclipse that of physicians over the next decade.

Advanced practice clinicians can also take over some of the routine work in a primary care practice, allowing physicians to focus on more clinically complex needs.

The report found geographic variation in the visit trends, which corresponds to differences in scope of practice and licensing laws between states. Some states afford NPs and PAs full practice authority, allowing them to operate independently, while others require physician oversight.

Hargraves said, though, that states with a slower level of growth in visits to NPs and PAs in the report don’t necessarily have the most restrictive laws for these providers. Visits in New Mexico, for example, grew by 37%, while in Massachusetts they grew by 285%, as visits to these clinicians were already higher.

“The growth doesn’t always mean that low growth is in more restrictive [locations],” Hargraves said.

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However, the report did indicate that visits to primary care physicians were not fully offset by the increase in visits to other clinicians. In 2012, visits to primary care doctors accounted for 51% of visits, which decreased to 43% in 2016.

An increase in visits to NPs and PAs accounted for less than half (43%) of that differential. This is likely because not all NPs and PAs operate in primary care facilities, according to the report, so some patients may have sought specialty care from those providers.

The report also looks into the cost differences between these two types of providers. Visits to primary care physicians cost about the same on average ($106) as visits to an advanced practice provider ($103), so the report didn’t flag significant cost savings between the two.

Hargraves said that the researchers were surprised by this finding, as part of the argument for deploying more NPs and PAs is that doing so saves money.

“This sort of cost savings argument—we didn’t find that,” he said, “but looking at the areas where there’s larger increase in NP and PA office visits, it lines up with some of primary care shortage areas, so the access-to-care piece definitely seems to be supported.”