Variations in Nurse Practitioner full practice authority in the United States: Difference in difference analysis of access and health Performance at a national level

Background: Authority over healthcare professional regulation in the United States rests with individual states, resulting in varied timelines and approaches to granting nurse practitioners (NPs) full practice authority (FPA). The impact of these policy changes on healthcare utilization and patient outcomes remains unclear. Objective: To evaluate the effect of NP full practice authority on healthcare access and patient outcomes across U.S. states. Methods: We applied a staggered difference-in-differences model using data from state legal statutes and the Medical Expenditure Panel Survey (1997-2018). Analyses included all 50 states and the District of Columbia to assess changes in healthcare utilization-specifically, NP-provided primary care visits, physician visits, and emergency department (ED) use-before and after FPA enactment. Results: States adopting NP full practice authority experienced a modest but significant increase in NP primary care visits without a corresponding decline in physician visits. Additionally, non-urgent ED utilization decreased in states with FPA, suggesting improved access to primary care. Patient-reported activities of daily living improved modestly, indicating potential health benefits associated with expanded NP authority. Conclusions: Granting full practice authority to nurse practitioners enhances access to care, optimizes healthcare utilization, and may yield modest improvements in patient outcomes. These findings support the role of FPA policies in strengthening the primary care workforce while maintaining quality of care. Future research should explore long-term impacts and broader health system effects as additional states implement or modify FPA legislation.