Emergency department and inpatient service utilization among hospitalized patients with substance use disorder and experiences of homelessness

Background: In the last decade, hospital service utilization and associated costs have increased. Both substance use and housing instability are associated with negative health outcomes. Because experiences of homelessness are prevalent among individuals with substance use disorders, this study sought to assess the role of homelessness in healthcare service utilization among hospitalized patients with diagnosed substance use disorders.

Methods: Healthcare service utilization were abstracted from a regional health information exchange in Maryland, United States and examined for all participants enrolled in the NavSTAR trial (n=400). Homelessness status was based on self-report during the index hospitalization and included reports of unsheltered living, living in shelters, or doubling up. Propensity score weighted Cox regression survival analysis for recurrent events was used to assess differences in risk for healthcare service utilization comparing those experiencing homelessness to those that were stably housed.

Results: Compared to those that were stably housed, experiences of homelessness were associated with increased risk of any hospital encounter (i.e., inpatient admission and/or emergency department visits) within 12 months of follow-up (hazard ratio [HR]=1.72, 95% confidence interval [CI]=1.13, 2.62). Homelessness was also associated with increased risk of both medical and psychiatric emergency department visits through 12-month follow-up (medical ED HR=1.99, 95% CI=1.16-3.40; psychiatric ED HR=3.93, 95% CI=1.54-10.04).

Conclusion: While controlling for comorbid substance use and mental health diagnoses, homelessness was associated with increased risk of hospital utilization within 12-month follow-up, particularly emergency department utilization. This increased risk could be driven by unmet needs related to housing instability that impose barriers to addressing basic needs and accessing routine healthcare. Future research is needed to develop and validate targeted assessment and intervention on housing instability that could be integrated into healthcare settings like hospitals to reduce this risk and facilitate linkage to housing resources.