Medicaid Expansion of Opioid Use Disorder Treatment and Overdose Mortality in Vermont

• In Event: Regulating Risk: State Policy and Health Outcomes Across Substance Use and Reproductive Care

Abstract

Research Objective

The opioid epidemic has been a leading cause of mortality in the United States, disproportionately affecting adults of low socioeconomic status. Expanding access to medications for opioid use disorder (MOUD) has been a central policy goal, with Medicaid playing a critical role as the primary payer for low-income adults and the largest payer of substance use disorder treatment. Vermont's 2013 hub-and-spoke program reorganized OUD treatment into a statewide network pairing regional specialty hubs with primary care spokes, directly addressing the fragmentation widely cited as constraining treatment delivery elsewhere. Along with Vermont’s ACA Medicaid expansion in 2014, the program achieved treatment penetration rates far exceeding national averages. This study examines the impact of Vermont's hub-and-spoke program on opioid overdose mortality and whether effects differed by socioeconomic status.

Methods

The study period spanned 1999 to 2022, with a pre-implementation period from 1999 to 2012 and a post-implementation period from 2013 to 2022. The primary outcome was opioid overdose mortality among adults ages 15–64, obtained from restricted-use cause-of-death records from the National Center for Health Statistics. We also analyzed state-year measures of MOUD utilization, including buprenorphine and extended-release naltrexone prescribing rates in Medicaid from 2010 to 2022, derived from Medicaid State Drug Utilization Data and denominated by Medicaid enrollment estimates from the American Community Survey.

Our primary analysis used a difference-in-differences event study to compare annual changes in opioid overdose mortality in Vermont relative to all other U.S. states, with census division-by-year fixed effects to account for regional heterogeneity in fentanyl diffusion. To address inference challenges arising from a single treated unit, we used randomization inference to assess statistical significance. We further examined heterogeneity by educational attainment as a proxy for socioeconomic status using a triple difference-in-differences event study.

Findings

Vermont's hub-and-spoke program and Medicaid expansion were associated with large increases in Medicaid buprenorphine prescribing after 2013 relative to other states, with no corresponding increase in extended-release naltrexone. Vermont's opioid overdose mortality trajectory diverged sharply from the placebo distribution beginning in 2014, reaching a peak estimated reduction of 14.53 deaths per 100,000 in 2016. Cumulative mortality reductions total approximately 300 fewer opioid overdose deaths over the 2013–2020 period. Effects were concentrated among adults without a four-year college degree, with no corresponding reductions among college graduates. Effects attenuated after 2020 and reversed by 2022, coinciding with the COVID-19 pandemic and the accelerating national shift toward polysubstance overdose deaths.

Conclusions

Vermont's coordinated Medicaid expansion and hub-and-spoke delivery system reform was associated with sustained reductions in opioid overdose mortality concentrated among low-socioeconomic status adults. These findings provide evidence that expanding access to OUD treatment through delivery system reforms financed by Medicaid expansion can produce meaningful reductions in population-level overdose mortality.

Author

• Sabin Gaire, University of Pittsburgh
  Presenting Author