Nurse Practitioner Independence, Health Care Utilization, and Health Outcomes

Implementation of the Affordable Care Act is expected to increase demand for medical services across the U.S., particularly the demand for primary care.  The ACA contains a number of provisions designed to increase the amount of primary care consumed in the U.S., including mandating coverage for preventive services, funding community disease prevention measures, and increasing the number of primary care providers.  Traditionally, physicians have been the health care professionals responsible for providing primary care.  But as new physicians increasingly choose to become specialists, a greater percentage of primary care is being provided by non-physicians.  In 2010, nurse practitioners (NPs) were the largest group of non-physician primary care providers, with the approximately 56,000 NPs in primary care representing 19% of all primary care providers.

               State scope-of-practice laws regulate the types of medical services that NPs can provide and the necessary level of physician involvement in NP practice. Most notably, some states allow NPs to both practice and prescribe drugs without physician supervision, effectively enabling them to be independent providers of primary care services.  Scope-of-practice laws represent an important policy tool through which states can influence the total amount of preventive care provided, the provision of medical care in rural areas, and potentially overall medical care costs.  In early 2012, over 50 bills were under consideration in state legislatures across the U.S. that would affect scope-of-practice laws for NPs.  However, little is known about the effect of allowing NPs to be independent primary care providers on the utilization of primary care and population health outcomes.

               We estimate the causal effect of NP independence on population utilization of care and health outcomes by exploiting plausibly exogenous state level variation in the timing of changes in regulations governing the level of supervision that doctors must provide for NPs.  We obtain individual level data on health care utilization and outcomes from the Medical Expenditure Panel Survey.  As states have allowed NPs to practice or prescribe independently for different lengths of time, we use an event study approach to investigate the difference between short and long run effects of NP independence.

               We find that states that allow NPs to practice and prescribe without physician supervision see increases in health care utilization and care quality, with utilization increases primarily coming from adults while quality improvements impact both adults and children.  These increases have positive effects on self-reported health status.  Patients with conditions that respond to primary care show reductions in emergency room use, suggesting both an improvement in health and cost savings in the provision of care.  The response to NP independence shows little heterogeneity across the population, so the gains in health outcomes are widespread.  Our evidence suggests that the primary mechanisms for these changes are the elimination of physician and NP time spent on supervision and decreases in indirect costs of receiving medical care such as better appointment availability and lower patient travel costs, rather than changes in provider supply or composition.