Nonadherence to medications is costly and improving adherence is difficult, requiring multifactorial solutions, including policy solutions.
The purpose of this study is to evaluate the effect of one policy strategy on medication adherence. Specifically, we examine the effect on adherence of expanding scope-of-practice regulations for nurse practitioners (NPs) to practice and prescribe without physician supervision.
We conducted three difference-in-difference multivariable analyses of commercial insurance claims.
Patients who filled at least two prescriptions in one of three chronic therapeutic medications: anti-diabetics (n = 514,255), renin angiotensin system antagonists (RASA) (n = 1,679,957), and anti-lipidemics (n = 1,613,692).
Medication adherence was measured as the proportion of days covered (PDC). We used one continuous (PDC 0–1) and one binary outcome (PDC of > .8), the latter indicating good adherence.
Patients taking anti-diabetic medications had a 1.9 percentage point higher medication adherence rate (p < 0.05) and a 2.7 percentage point higher probability of good adherence (p < 0.001) in states that expanded NP scope-of-practice. Medication adherence for patients taking RASA was higher by 2.3 percentage points (p < 0.001) and 3.4 percentage points (p < 0.01) for both measures, respectively. Patients taking anti-lipidemics saw a smaller, but statistically insignificant, improvement in adherence.
Results indicate that scope-of-practice regulations that allow NPs to practice and prescribe without physician oversight are associated with improved medication adherence. We postulate that the mechanism for this effect is increased access to health care services, which in turn increases access to prescriptions. Our results suggest that policies allowing NPs to maximally use their skills can be beneficial to patients.
This is a preview of subscription content, log in to check access.
Buy single article
Instant access to the full article PDF.
Price includes VAT for USA
Subscribe to journal
Immediate online access to all issues from 2019. Subscription will auto renew annually.
This is the net price. Taxes to be calculated in checkout.
Luga AO, McGuire MJ. Adherence and health care costs. Risk Manag Healthc Policy 2014;7:35-44. doi:https://doi.org/10.2147/RMHP.S19801
Osterberg L, Blaschke T. Adherence to Medication. N Engl J Med 2005;353(5):487-497. doi:https://doi.org/10.1056/NEJMra050100
Aitken M, Valkova S. The $200 Billion Opportunity from Using Medicines More Responsibly. Parsippany: IMS Institute for Healthcare Informatics; 2013.
Medicare Payment Advisory Commission. A Databook: Healthcare Spending and the Medicare Program. Washington, DC: Medicare Payment Advisory Commission; 2016. http://www.medpac.gov/docs/default-source/data-book/june-2016-data-book-health-care-spending-and-the-medicare-program.pdf.
Zullig LL, Granger BB, Bosworth HB. A renewed Medication Adherence Alliance call to action: harnessing momentum to address medication nonadherence in the United States. Patient Prefer Adherence 2016;10:1189-1195. doi:https://doi.org/10.2147/PPA.S100844
U.S. Department of Health and Human Services, Health Resources and Services Administration (HRSA), National Center for Health Workforce Analysis. Projecting the Supply and Demand for Primary Care Practitioners Through 2020. Rockville, Maryland: U.S. Department of Health and Human Services; 2013. https://bhw.hrsa.gov/sites/default/files/bhw/nchwa/projectingprimarycare.pdf. Accessed 9 Feb 2016.
AAMC. The Complexities of Physician Supply and Demand: Projections from 2013 to 2025. Prepared for the Association of American Medical Colleges. Washington, DC: Association of American Medical Colleges; 2015.; 2015. https://www.aamc.org/download/426242/data/ihsreportdownload.pdf?cm_mmc=AAMC-_-ScientificAffairs-_-PDF-_-ihsreport. Accessed 9 June 2016.
Spetz J Expanding the Role of Nurse Practitioners in California. Physician Oversight in Other States. California Health Care Foundation; 2019. https://www.chcf.org/wp-content/uploads/2019/05/ExpandingNPOversightStates.pdf.
Buerhaus P, Perloff J, Clarke S, O’Reilly-Jacob M, Zolotusky G, DesRoches CM. Quality of Primary Care Provided to Medicare Beneficiaries by Nurse Practitioners and Physicians. Med Care 2018. doi:https://doi.org/10.1097/MLR.0000000000000908
Kurtzman ET, Barnow BS. A Comparison of Nurse Practitioners, Physician Assistants, and Primary Care Physicians’ Patterns of Practice and Quality of Care in Health Centers. Med Care 2017;55(6):615-622. doi:https://doi.org/10.1097/MLR.0000000000000689
Lenz ER, Mundinger MO, Kane RL, Hopkins SC, Lin SX. Primary Care Outcomes in Patients treated by Nurse Practitioners or Physicians: Two-Year Follow-Up. Med Care Res Rev 2004;61(3):332-351. doi:https://doi.org/10.1177/1077558704266821
Newhouse RP, Stanik-Hutt J, White KM, et al. Advanced Practice Nurse Outcomes 1990-2008: A Systematic Review. Nurs Econ 2011;29(5):1.
Stanik-Hutt J, Newhouse RP, White KM, et al. The Quality and Effectiveness of Care Provided by Nurse Practitioners. Jnp-J Nurse Pract. 2013;9(8):492-+. doi:https://doi.org/10.1016/j.nurpra.2013.07.004
Muench U, Guo C, Thomas CP, Perloff J. Adherence, ER Visits and Costs of Nurse Practitioner and Primary Care Physician Patients: Evidence from Three Cohorts of Medicare Beneficaries. Forthcom Health Serv Res. 2018.
Park J, Athey E, Pericak A, Pulcini J, Greene J. To What Extent Are State Scope of Practice Laws Related to Nurse Practitioners’ Day-to-Day Practice Autonomy? Med Care Res Rev 2018;75(1):66-87. doi:https://doi.org/10.1177/1077558716677826
American Medical Association. State Law Chart: Nurse Practitioner Prescriptive Authority.; 2017. https://www.ama-assn.org/sites/ama-assn.org/files/corp/media-browser/specialty%20group/arc/ama-chart-np-prescriptive-authority.pdf.
Kurtzman ET, Barnow BS, Johnson JE, Simmens SJ, Infeld DL, Mullan F. Does the Regulatory Environment Affect Nurse Practitioners’ Patterns of Practice or Quality of Care in Health Centers? Health Serv Res 2017;52:437-458. doi:https://doi.org/10.1111/1475-6773.12643
Ortiz J, Hofler R, Bushy A, Lin Y-L, Khanijahani A, Bitney A. Impact of Nurse Practitioner Practice Regulations on Rural Population Health Outcomes. Healthcare. 2018;6(65). doi:https://doi.org/10.3390/healthcare6020065
Perloff J, Clarke S, DesRoches CM, O’Reilly-Jacob M, Buerhaus P. Association of State-Level Restrictions in Nurse Practitioner Scope of Practice With the Quality of Primary Care Provided to Medicare Beneficiaries. Med Care Res Rev 2017:1077558717732402. doi:https://doi.org/10.1177/1077558717732402
Kleiner MM, Marier A, Park KW, Wing C. Relaxing Occupational Licensing Requirements: Analyzing Wages and Prices for a Medical Service. J Law Econ 2016;59(2):261-291. doi:https://doi.org/10.1086/688093
Graves JA, Mishra P, Dittus RS, Parikh R, Perloff J, Buerhaus PI. Role of Geography and Nurse Practitioner Scope-of-Practice in Efforts to Expand Primary Care System Capacity: Health Reform and the Primary Care Workforce. Med Care 2016;54(1):81-89. doi:https://doi.org/10.1097/MLR.0000000000000454
Kalist DE, Spurr SJ. The effect of state laws on the supply of advanced practice nurses. Int J Health Care Finance Econ 2004;4(4):271–281.
Kuo Y-F, Loresto FL, Rounds LR, Goodwin JS. States with the least restrictive regulations experienced the largest increase in patients seen by nurse practitioners. Health Aff (Millwood) 2013;32(7):1236-1243. doi:https://doi.org/10.1377/hlthaff.2013.0072
Stange K. How does provider supply and regulation influence health care markets? Evidence from nurse practitioners and physician assistants. J Health Econ 2014;33:1-27. doi:https://doi.org/10.1016/j.jhealeco.2013.10.009
Whaley C, Muench U, Spetz J. The Effects of Nurse Practitioner Scope of Practice Laws on Healthcare Spending, Prices, and Access. RR Med Care Res Rev 2018.
Koch T, Petek N. The Effect of Nurse Practitioner Scope of Practice Laws on Health Care Utilization and Health: Evidence from Law Changes and Patient Moves. Fed Trade Comm Work Pap 2019.
Spetz J, Parente ST, Town RJ, Bazarko D. Scope-Of-Practice Laws For Nurse Practitioners Limit Cost Savings That Can Be Achieved In Retail Clinics. Health Aff (Millwood) 2013;32(11):1977-1984. doi:https://doi.org/10.1377/hlthaff.2013.0544
Traczynski J, Udalova V. Nurse practitioner independence, health care utilization, and health outcomes. J Health Econ 2018;58:90-109. doi:https://doi.org/10.1016/j.jhealeco.2018.01.001
Alexander D, Schnell M. Just What the Nurse Practitioner Ordered: Independent Prescriptive Authority and Population Mental Health. Rochester: Social Science Research Network; 2018. https://papers.ssrn.com/abstract=2985991. Accessed September 3, 2018.
Hamilton MR. Three Essays in Health Economics. Univeristy of Michigan; 2017. https://deepblue.lib.umich.edu/bitstream/handle/2027.42/138556/hamiltmr_1.pdf?sequence=1&isAllowed=y. Accessed 2 June 2018.
Alexander D, Schnell M. Just what the nurse practitioner ordered: Independent prescriptive authority and population mental health. J Health Econ 2019;66:145-162. doi:https://doi.org/10.1016/j.jhealeco.2019.04.004
Balkrishnan R, Rajagopalan R, Camacho FT, Huston SA, Murray FT, Anderson RT. Predictors of medication adherence and associated health care costs in an older population with type 2 diabetes mellitus: a longitudinal cohort study. Clin Ther 2003;25(11):2958-2971.
Karve S, Markowitz M, Fu D-J, et al. Assessing Medication Adherence and Healthcare Utilization and Cost Patterns Among Hospital-Discharged Patients with Schizoaffective Disorder. Appl Health Econ Health Policy 2014;12(3):335-346. doi:https://doi.org/10.1007/s40258-014-0095-8
Pittman DG, Tao Z, Chen W, Stettin GD. Antihypertensive medication adherence and subsequent healthcare utilization and costs. Am J Manag Care 2010;16(8):568-576.
Roebuck MC, Liberman JN, Gemmill-Toyama M, Brennan TA. Medication adherence leads to lower health care use and costs despite increased drug spending. Health Aff (Millwood) 2011;30(1):91-99. doi:https://doi.org/10.1377/hlthaff.2009.1087
Lau DT, Briesacher BA, Touchette DR, Stubbings J, Ng JH. Medicare Part D and Quality of Prescription Medication Use. Drugs Aging 2011;28(10):797-807. doi:https://doi.org/10.2165/11595250-000000000-00000
Vrijens B, De Geest S, Hughes DA, et al. A new taxonomy for describing and defining adherence to medications. Br J Clin Pharmacol 2012;73(5):691-705. doi:https://doi.org/10.1111/j.1365-2125.2012.04167.x
American Association of Nurse Practitioners. What’s an NP? https://www.aanp.org/all-about-nps/what-is-an-np#unique-approach. Published 2018. Accessed 30 Aug 2018.
Wroth TH, Pathman DE. Primary Medication Adherence in a Rural Population: The Role of the Patient-Physician Relationship and Satisfaction with Care. J Am Board Fam Med 2006;19(5):478-486. doi:https://doi.org/10.3122/jabfm.19.5.478
Schoenthaler A, Chaplin WF, Allegrante JP, et al. Provider communication effects medication adherence in hypertensive African Americans. Patient Educ Couns 2009;75(2):185-191. doi:https://doi.org/10.1016/j.pec.2008.09.018
Harmon G, Lefante J, Krousel-Wood M. Overcoming barriers: the role of providers in improving patient adherence to antihypertensive medications. Curr Opin Cardiol 2006;21(4):310–315. doi:https://doi.org/10.1097/01.hco.0000231400.10104.e2
Viswanathan M, Golin CE, Jones CD, et al. Interventions to improve adherence to self-administered medications for chronic diseases in the United States: a systematic review. Ann Intern Med 2012;157(11):785-795. doi:https://doi.org/10.7326/0003-4819-157-11-201212040-00538
Piette JD, Heisler M, Krein S, Kerr EA. The Role of Patient-Physician Trust in Moderating Medication Nonadherence Due to Cost Pressures. Arch Intern Med 2005;165(15):1749-1755. doi:https://doi.org/10.1001/archinte.165.15.1749
Martin LR, Williams SL, Haskard KB, DiMatteo MR. The challenge of patient adherence. Ther Clin Risk Manag 2005;1(3):189-199.
Horrocks S, Anderson E, Salisbury C. Systematic review of whether nurse practitioners working in primary care can provide equivalent care to doctors. BMJ. 2002;324(7341):819-823. doi:https://doi.org/10.1136/bmj.324.7341.819
Kinnersley P, Anderson E, Parry K, et al. Randomised controlled trial of nurse practitioner versus general practitioner care for patients requesting “same day” consultations in primary care. BMJ. 2000;320(7241):1043-1048. doi:https://doi.org/10.1136/bmj.320.7241.1043
Muench U, Perloff J, Thomas CP, Buerhaus PI. Prescribing Practices by Nurse Practitioners and Primary Care Physicians: A Descriptive Analysis of Medicare Beneficiaries. J Nurs Regul 2017;8(1):21-30.
Pharmacy Quality Allience. PQA Measure Overview. Virginia: PQA Alliance; 2019. https://www.pqaalliance.org/assets/Measures/2019_PQA_Measure_Overview.pdf.
Centers for Medicare & Medicaid Services (CMS). Medicare 2018 Part C & D Star Ratings Technical Notes.; 2017. https://www.cms.gov/Medicare/Prescription-Drug-Coverage/PrescriptionDrugCovGenIn/Downloads/2018-Star-Ratings-Technical-Notes-2017_09_06.pdf.
Pharmacy Quality Allience. PQA Measures Used By CMS in the Star Ratings & As Display Ratings Program. http://pqaalliance.org/measures/cms.asp. Published 2017. Accessed 5 Oct 2017.
Pharmacy Quality Alliance. Measure Licensing & Use. https://pqa.memberclicks.net/measure-licensing-use. Published 2018. Accessed 15 March 2020
Pearson L. The Pearson Report. Am J Nurse Pract 2009;13(2):8-82.
Pearson L. 24th Annual Legislative Update. Nurs Pract 2012;37(1):22–45.
National Quality Forum. Proportion of Days Covered (PDC): 3 Rates by Therapeutic Category. http://goo.gl/MjyDAC. Published 2014. Accessed 1 Nov 2014.
Roebuck MC, Kaestner RJ, Dougherty JS. Impact of Medication Adherence on Health Services Utilization in Medicaid. Med Care 2018;56(3):266-273.
Phillips SJ. 25th Annual Legislative Update. Nurs Pract 2013;38(1):18–42.
Dimick JB, Ryan AM. Methods for Evaluating Changes in Health Care Policy: The Difference-in-Differences Approach. JAMA. 2014;312(22):2401-2402. doi:https://doi.org/10.1001/jama.2014.16153
Imbens GW, Wooldridge JM. Recent Developments in the Econometrics of Program Evaluation. J Econ Lit 2009;47(1):5-86. doi:https://doi.org/10.1257/jel.47.1.5
Laurant M, Harmsen M, Wollersheim H, Grol R, Faber M, Sibbald B. The Impact of Nonphysician Clinicians. Med Care Res Rev. 2009;66(6_suppl):36S-89S. doi:https://doi.org/10.1177/1077558709346277
Naylor MD, Kurtzman ET. The Role Of Nurse Practitioners In Reinventing Primary Care. Health Aff (Millwood). 2010;29(5):893-899. doi:https://doi.org/10.1377/hlthaff.2010.0440
Swan M, Ferguson S, Chang A, Larson E, Smaldone A. Quality of primary care by advanced practice nurses: a systematic review. Int J Qual Health Care 2015;27(5):396-404. doi:https://doi.org/10.1093/intqhc/mzv054
Jiao S, Murimi IB, Stafford RS, Mojtabai R, Alexander GC. Quality of Prescribing by Physicians, Nurse Practitioners, and Physician Assistants in the United States. Pharmacotherapy. 2018. doi:https://doi.org/10.1002/phar.2095
Ladd E, Sweeney CF, Guarino A, Hoyt A. Opioid Prescribing by Nurse Practitioners in Medicare Part D: Impact of State Scope of Practice Legislation. Med Care Res Rev 2017. doi:https://doi.org/10.1177/1077558717725604
Muench U, Guo C, Thomas C, Perloff J. Medication adherence, costs, and ER visits of nurse practitioner and primary care physician patients: Evidence from three cohorts of Medicare beneficiaries. Health Serv Res 2019;54(1):187-197. doi:https://doi.org/10.1111/1475-6773.13059
This study was in part funded by the Laura and John Arnold Foundation through a grant from the Health Care Cost Institute and National Academy for State Health Policy.
Conflict of Interest
The authors declare that they do not have a conflict of interest.
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Electronic Supplementary Material
About this article
Cite this article
Muench, U., Whaley, C., Coffman, J. et al. Scope-of-Practice for Nurse Practitioners and Adherence to Medications for Chronic Illness in Primary Care. J GEN INTERN MED (2020). https://doi.org/10.1007/s11606-020-05963-3
- medication adherence
- nurse practitioners
- policy evaluation
- administrative claims data