Background: The utilization of Nurse Practitioners (NPs) has emerged as a potential solution to address physician shortages, serve underserved areas, and manage high patient volumes in primary care settings. However, the scope of practice (SOP) laws for NPs varies significantly across states. Twenty-eight states and Washington D.C. allow full practice authority; twelve states have reduced practice regulations; and eleven states have restricted practice. This variation in regulatory frameworks, coupled with the cost-effectiveness of NPs compared to physicians, necessitates a comprehensive examination of the impact of NP SOP laws on health outcomes. As the United States faces an impending physician shortage, understanding the relationship between NP SOP and healthcare quality becomes crucial for informed policy decisions and effective workforce planning in primary care.

Methods: A legal epidemiology study was conducted to analyze the impact of Nurse Practitioner (NP) scope of practice (SOP) laws across five U.S. states: Oregon, Washington, California, Texas, and Illinois, representing a spectrum of regulatory frameworks. The study began by defining the research question on how NP SOP laws affect primary care outcomes. A comprehensive legal mapping process followed, involving the collection and coding of relevant laws from state legislatures to identify patterns and variations. Primary care health outcome data, including wait times, provider-to-population ratios, and mortality rates, were collected for each state. The analysis phase compared the coded legal data with health outcomes to assess the impact of different SOP laws.

Results: States with the highest number of NPs (approximately 20,000) tended to have the most restrictive SOP laws, while states with the lowest NP populations (around 2,000) had full SOP laws. States with full SOP demonstrated better primary care physician (PCP) to population ratios, ranging from 89.1 to 101.1 per 100,000 residents. No clear trends emerged regarding mortality rates and NP SOP laws. However, states with restricted SOP had the shortest PCP wait times, while full SOP states had the longest wait times.

Conclusion: Full SOP for NPs can increase primary care access but does not necessarily improve mortality rates. Larger states face challenges in regulating full SOP NPs, possibly explaining why they have higher restrictions. Traditionally restrictive states like California and Texas are now considering bills to grant full SOP to NPs. This shift suggests a growing recognition of NPs' potential increase primary care access, highlighting the ongoing evolution of healthcare policy as states seek to balance professional regulation with the need for expanded primary care access to overcome the physician shortage.