How will a healthcare system already short on clinicians respond to the increase in demand that will come with greater numbers of insured patients? While the ACA contains provisions to help increase the work force, those take time to implement, and it's reasonable to expect that hospitals and clinics will experience increased patient loads. But nobody is certain how the increased demand will manifest itself, said Christine Everett, PhD, MPH, PA-C, director of research for the University of Wisconsin.

"Until we really see full implementation of any changes, it's uncertain as to what direction things will go," Everett said. "I think that when they were designing the ACA, they took what happened in Massachusetts to heart. In hindsight, it was probably reasonable that once you gave people access to care, they'd start utilizing it more. Massachusetts had a flood of people that wanted to utilize [the healthcare system] and didn't have the structure in place to care for them."

The Affordable Care Act contains provisions intended to help clinicians handle the increase in patients, such as funding for electronic health records, clinician training and community health centers, Everett said. A May 2009 study published in the journal Health Affairs noted that between fall of 2006 and fall of 2008 in Massachusetts, the likelihood of working-age adults (ages 18-64) having visited any physician in the past 12 months increased 5.7%, and the likelihood of adults having had a preventive care visit in the past 12 months increased 6.5%. Gains were strongest for lower-income adults, or those with incomes less than 300% of the federal poverty level, the study said.

As in Massachusetts, the healthcare system nationwide will likely see the effects initially of pent-up demand, said Rod Hooker, PA-C, senior research director at the Lewin Group in Falls Church, Va. "That means that 30 million people who theoretically have gone without healthcare will on a certain date have access," Hooker said. "Where will they go? They'll turn to whomever is available." That could mean a nearby practice, urgent care clinics or emergency rooms, Hooker said. "Some patients will feel emboldened to go wherever they want."

But the healthcare system in Massachusetts eventually adjusted, and demand has fallen back to pre-reform levels, said Hooker. "After 2 years, the pent-up demand had been managed," Hooker said. "Those who didn't have insurance and now have insurance seem to be getting care in the same way as those who did have insurance. Massachusetts has ramped up its use of PAs and NPs and implemented primary care medical homes. We don't have the data yet, but one guess is that they're making better use of PAs and NPs in providing access."

A similar utilization pattern is often seen in patients who have just begun to receive Medicare, Everett said. Initially, their utilization is higher-than-average for the first year or so, perhaps because of conditions that had not been treated or services that were not covered under the patient's previous insurance. After the initial increase, utilization becomes more even, Everett said.

Everett and Hooker, in a study published in the September-October 2011 issue of Public Health Reports, noted that a shortage of 124,000 primary care physicians is anticipated by 2025. In the same study, Everett and Hooker predicted that the overall supply of PAs will reach nearly 128,000 by 2025.

While the physician shortage persists and will continue for some time, the way care is provided also continues to evolve. "The traditional way we estimate how many physicians we will need is based on an older model and not on team-based care," Everett said. "We already know we're going to be short of physicians. That's going to mean more opportunity for PAs."