Inpatient utilization among Medicaid members with substance use disorder in Oregon

In the United States, substance use disorders (SUDs) remain a critical public health concern with significant morbidity and mortality. Oregon exemplifies this crisis with high rates of illicit drug use and overdose deaths, compounded by systemic challenges like behavioral health workforce shortages. This study's objective is to characterize patterns of acute care utilization and ED visit and admission reasons among Medicaid enrollees with opioid use disorder, stimulant use disorder, and/or unintentional substance overdoses in the Portland metro area.

We conducted a cross-sectional analysis of 2023 Medicaid enrollment and claims data from Health Share of Oregon, a coordinated care organization. The study included adult Medicaid members (aged 18 to 65) enrolled in Health Share of Oregon for at least six months during 2023, categorized into cohorts based on ICD-10-CM diagnosis codes for opioid use disorder, stimulant use disorder, and unintentional substance overdoses. Members without these diagnoses served as a comparison group. Measures included rates per 1,000 member months, frequencies, and proportions of emergency department (ED) visits, avoidable ED visits, inpatient admissions, length of stay, readmissions, and hospitalizations for ambulatory care sensitive conditions, as well as reasons for ED visits and inpatient admissions.

Compared to non-cohort members, individuals in the cohorts had significantly higher emergency department and inpatient utilization rates. Those with unintentional substance overdoses exhibited the highest rates. Cohort members had longer hospital stays, higher rates of 30-day readmissions, and increased avoidable ED visits and hospitalizations for ambulatory care sensitive conditions. Infection was identified as the most common reason for admission among cohort members.

Medicaid enrollees with substance use disorders exhibit substantial acute care needs and face systemic challenges. Addressing these needs requires enhanced access to evidence-based SUD treatments across multiple care settings. These findings underscore the need for clinical and policy interventions to mitigate the intertwined crises of SUD and acute care conditions in vulnerable populations.