Background: Unhoused individuals experience disproportionately high rates of emergency department (ED) use, reflecting reliance on EDs for care due to limited access to healthcare or insurance. While population-based studies focused on houseless individuals have shown high rates of ED usage, few have examined patterns of repeated EDs utilization and escalation of care intensity with housed peers. 

Methods: We conducted a retrospective age and gender matched cohort study using the PearlDiver Mariner database, to evaluate the associations between houselessness and ED utilization. Unhoused were identified using  ICD-10-D code Z59.0, and matched 1:1 to housed controls aged 18-70 years.  ED and inpatient utilization were captured over a two-year follow up period using CPT codes for emergency encounters. Utilization frequency was stratified into increasing thresholds (≥5, ≥10, ≥20 and ≥50 encounters) to assess patterns of use. Chi-square tests compared utilization distribution between cohorts, and t-tests evaluated differences in age. Stratified analyses were conducted to assess demographic balance within higher-utilization subgroups. 

Results: Among the 170,937 individuals that met inclusion criteria, unhoused individuals demonstrated significantly higher ED utilization across all examined thresholds of repeated use. Unhoused individuals had greater odds of ≥ 5 ED encounters (OR = 5.06, p < 0.001), ≥10 encounters (OR = 5.62, p < 0.001), and ≥25 encounters. (OR = 6.68, p < 0.001). At the most extreme threshold of ≥ 50 encounters included 3.5% of unhoused individuals, and this represented over 30-fold higher risk compared to housed peers. Age disparities widened with increasing ED utilization, while gender differences varied by threshold. 

Conclusions: Housing instability is strongly associated with ED utilization, and unhoused individuals are a disproportionately affected ED-utilizing population, underscoring the need for structural interventions and systemic change.