Understanding Overdose Risk: The Role of System-level Factors after a Non-Fatal Drug Overdose Event

This dissertation examined how system-level factors influence subsequent overdose recurrence, medication for opioid use disorder (MOUD) retention, and geographic disparities in harm reduction and treatment service availability. In Chapter 2, a scoping review was conducted to understand the landscape of post-overdose interventions by examining the timing of engagement, care coordination, and continuity of care. Majority of post-overdose interventions initially made contact with overdose survivors at the emergency department (45%) and included structured efforts to connect overdose survivors to treatment, harm reduction services, and social support. Care-coordination at the point of care was frequently practiced (86%), continuity of care was limited across our review (10%). In Chapter 3, a secondary data analysis was conducted using an 18-month longitudinal cohort study design to evaluate predictors of time to first MOUD discontinuation and subsequent non-fatal overdose. Overdose survivor status was significantly associated with time to first non-fatal overdose event (unadjusted hazard ratio = 4.24, 95% CI: 2.74-6.57, p < .001) and was not significantly associated with lower treatment discontinuation (hazard ratio (HR) = 1.09, 95% CI: 0.87-1.37). However, sociodemographic factors such as age, race/ethnicity, and insurance coverage were significantly strong predictors of MOUD discontinuation. In Chapter 4, a county-level geospatial and regression analysis across Tennessee (2018–2023) revealed that counties with syringe service program (SSP) were associated with higher fatal overdose incidence (adjusted incidence rate ratio, aIRR = 1.34, 95% CI: 1.16–1.55) when compared to counties without SSP. Furthermore, counties with high non-fatal overdose rates were strongly associated with fatal overdose incidence (aIRR = 1.0017, 95% CI: 1.0013–1.001). Opioid Treatment Program (OTP) presence and Office-Based Opioid Treatment (OBOT) provider availability were not significantly associated with fatal overdose rates in adjusted models. Across chapters, we examined system-level influences on overdose risk and MOUD retention, highlighting limited continuity of care in post-overdose interventions and the role of individual enabling factors such as age, insurance, race or ethnicity, and housing stability in shaping overdose and treatment discontinuation. At the ecological level, harm reduction programs are more often located in counties with already high fatal overdose rates, indicating targeted placement in high overdose burden counties.