The impact of substance use disorder and homelessness on hospital readmission

Background People experiencing homelessness and those with substance use disorder (SUD) are overrepresented in hospitalized populations. While homelessness and SUD are known to increase readmission, the impact of having both on readmission is unknown.Methods Retrospective analysis of adult inpatient admissions between October 2019 and October 2023 at an academic medical center in Boston, Massachusetts. We calculated rates of readmission to the same hospital within 30 days. We examined the effects of having a SUD diagnosis based on ICD-10 codes and homelessness based on ICD-10-CM code Z59.0×, being identified by hospital case management as homeless, or screening positive for housing instability.Results Among 164,280 inpatient encounters, 9.2% included any SUD diagnosis, 2.2% were noted to be currently unhoused, and 3.3% ever unhoused during the previous 12 months. Overall, 13.0% of patients were readmitted within 30 days. Readmission rates were higher among patients with current SUD compared to no SUD (16.7% vs. 12.6%, p < 0.001), patients currently unhoused (18.9% vs. 12.8%, p < 0.001), and unhoused in the past 12 months (20.1% vs. 12.7%, p < 0.001) compared to those with stable housing. After adjusting for age, race, gender, length of stay, and case severity, the adjusted rate ratio for patients with both SUD and homelessness was highest (ARR: 1.73), followed by patients with SUD only (ARR 1.33), and those experiencing homelessness only (ARR: 1.25) compared to patients with neither SUD or homelessness.Conclusions SUD and homelessness increase 30-day readmission. Hospital-based interventions are needed to address both addiction and housing instability.