Disparities in Emergency Medical Services Assessment of Unhoused Patients with Altered Mental Status

About this Research Project

Authors: K. Arrianna Thomson, MD¹; Caihan Tony Chen, EMT-B²; Naila Francies, EMT-P³, Andrea Elser, BA⁴; Soma De Bourbon, PhD⁵; Jonathan R. Powell, MPA, NRP⁶

¹Department of Emergency Medicine, Washington University, St. Louis, Missouri
²University of California, Los Angeles, Los Angeles, California
³Alameda County Emergency Medical Services Agency, Alameda, California
⁴Keck School of Medicine, University of Southern California, Los Angeles, California
⁵College of Social Sciences, San Jose State University, San Jose, California
⁶Clinical and Research Services, ImageTrend Inc., Eagan, Minnesota

Introduction

Altered mental status (AMS) is a high-risk reason for emergency medical services (EMS) activation, requiring thorough assessment to identify life-threatening but reversible causes. Whether these evaluations are delivered equitably across patient populations remains unclear. Prior studies suggest disparities in EMS care for people experiencing homelessness (PEH), but little is known about assessment in this context. Our objective was to evaluate whether PEH with AMS received comparable prehospital assessments to housed patients.

Methods

• We conducted a retrospective observational study using the 2024 ImageTrend Collaborate dataset.
• We included EMS activations from agencies that documented patient housing status in ≥50% of encounters and further selected cases with a primary impression of AMS.
• We evaluated documentation of four critical assessments: respiratory rate, systolic blood pressure, blood glucose, and pulse oximetry.
• A composite dichotomous variable captured whether all four assessments were completed.
• We used descriptive statistics (%, median) to examine patient demographics and multivariable logistic regression (Odds Ratio, 95% confidence interval) to examine the impact of housing status on assessment delivery, using Stata 18 MP for all analyses. 

Results

• We included 867,488 patient encounters from 22 agencies. With 22,928 of these identified as AMS encounters, 725 (3%) were PEH, 17,745 (77%) were housed, and 4,458 (20%) were missing housing status.
• PEH, compared to housed, had a younger median age (45 vs 68), an increased proportion of males (67% vs 52%), and an increased proportion of both Black (22% vs 18%) and Hispanic/Latino (12% vs 9%) patients.
• Compared to housed, PEH had lower documentation rates for systolic blood pressure (93% vs 97%), respiratory rate (80% vs 86%), blood glucose (80% vs 86%), and pulse oximetry (92% vs 95%).
• PEH had 41% (0.59 [0.4, 0.75]) lower odds of receiving all 4 assessments, controlling for patient age, gender, and race/ethnicity (Referent:Housed).  

Conclusion

Unhoused patients presenting with AMS were less likely to receive complete prehospital assessments, even after adjusting for demographic factors.  While study limitations exist, these findings raise concerns about systemic bias in EMS and underscore the need for both targeted and systemic interventions to ensure equitable prehospital care.