Acute Care Hospital Utilization Among Medical Inpatients Discharged With a Substance Use Disorder Diagnosis

Objective: Hospital discharge may be an opportunity to intervene among patients with substance use disorders to reduce subsequent hospital utilization. This study determined whether having a substance use disorder diagnosis was associated with subsequent acute care hospital utilization. Methods: We conducted an observational cohort study among 738 patients on a general medical service at an urban, academic, safety-net hospital. The main outcomes were rate and risk of acute care hospital utilization (emergency department visit or hospitalization) within 30 days of discharge. The main independent variable was presence of a substance use disorder primary or secondary discharge diagnosis code at the index hospitalization. Results: At discharge, 17% of subjects had a substance use disorder diagnosis. These patients had higher rates of recurrent acute care hospital utilization than patients without substance use disorder diagnoses (0.63 vs 0.32 events per subject at 30 days, P < 0.01) and increased risk of any recurrent acute care hospital utilization (33% vs 22% at 30 days, P < 0.05). In adjusted Poisson regression models, the incident rate ratio at 30 days was 1.49 (95% confidence interval, 1.12-1.98) for patients with substance use disorder diagnoses compared with those without. In subgroup analyses, higher utilization was attributable to those with drug diagnoses or a combination of drug and alcohol diagnoses, but not to those with exclusively alcohol diagnoses. Conclusions: Medical patients with substance use disorder diagnoses, specifically those with drug use-related diagnoses, have higher rates of recurrent acute care hospital utilization than those without substance use disorder diagnoses.