The Spillover Effects of NP Scope of Practice Expansions on Safety Net Participation: Evidence from WIC

• In Event: Implications of Scope of Practice Reform for Advanced Practice Registered Nurses

Abstract

Nurse practitioner (NP) scope of practice (SOP) expansions have been shown to improve access to healthcare, leading to direct health benefits. However, given that NPs are likely to practice in underserved areas, liberalizing SOP may also have spillover effects on safety net program participation, amplifying the health benefits of SOP expansion for underserved and underrepresented populations. Understanding and quantifying these spillovers is an important step in understanding the full implications of scope of practice liberalization for health equity and wellbeing.

In this paper, we study these spillovers by examining the effect of NP SOP expansion on enrollment in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC). Despite the well-known benefits of WIC enrollment, the program is highly underutilized; only 60% of individuals eligible for the program are enrolled. Access to independent NPs might improve WIC enrollment through reducing information costs, as providers and clinics often screen patients for safety net program eligibility. It may also reduce stigma associated with program enrollment, if providers can properly convey the benefits of program participation.

To estimate the effect of NP SOP expansion on WIC enrollment, we leverage the staggered rollout of full practice authority (FPA) for NPs across states using an event study framework with a difference-in-differences identification strategy. To account for the staggered rollout of FPA across states, we compute event study estimates using the approach described in Sun and Abraham (2021).

Using WIC administrative data from 2005-2019, we find that starting in years 4-5 after the implementation of NP FPA, WIC participation increases by 4.1% in treated states. The effect grows from that point, reaching 7.4% in years 8-9 post-FPA. We find that the increase in enrollment following NP FPA is highest for women and children, where we find effect sizes of 8.6% and 8.5% in years 8-9 post-FPA, respectively. These estimates imply that NP FPA leads to at least 22 additional monthly women enrollees and 192 additional children enrollees per 10,000 population in the long run.

Using data from the National Health Interview Survey, we show that the effect of NP FPA on WIC enrollment may be driven by improvements in access to care for the WIC-eligible population. These improvements in access to care reduce the information costs associated with WIC enrollment as clinics often screen patients for public program eligibility. Furthermore, we show that the effect may be driven by the nature of NPs in delivering patient-centered care through the nursing model, which may reduce the stigma associated with safety net program participation. In particular, we show that physician assistant remote practice authority, which exposes patients to a provider type not trained under the nursing model, has no effect on WIC enrollment.

Our results show that liberalizing scope of practice for nurse practitioners has spillover effects on safety net program participation. This suggests another pathway by which SOP expansion can improve the health and wellbeing of underserved populations.

Authors

• Owen Michael Fleming, Wayne State University
  Presenting Author

• Lilly Springer, University of Kansas
  Non-Presenting Co-Author