Differential associations between social determinants of health and the initiation of medications for opioid use disorder across care settings.

Timely initiation of medications for opioid use disorder (MOUD) remains a critical gap in the health-system response to the opioid crisis. Although social determinants of health (SDoH) influence treatment access, their impact may vary across care settings owing to differences in clinical workflows, regulatory constraints, and system-level processes. In this retrospective cohort study, we linked electronic health records from an integrated midwestern U.S. health system with neighborhood-level SDoH and area deprivation data to examine time to MOUD initiation among patients diagnosed with opioid use disorder between 2020 and 2024. Using inverse-probability-of-censoring-weighted Cox proportional hazards models with care-setting-specific effects, we found that SDoH associations with MOUD initiation were concentrated in the outpatient setting and differed significantly across settings: a greater neighborhood share of racial or ethnic minority residents was associated with slower outpatient initiation, whereas inpatient initiation was driven primarily by clinical complexity and emergency-department initiation showed limited sensitivity to neighborhood context. These patterns were robust to adjustment for informative censoring and to follow-up length. By linking geospatial social context to routine EHR data, this approach enables scalable, care-setting-specific surveillance of treatment inequities and can inform resource allocation to accelerate equitable delivery of addiction treatment.