Racial and Socioeconomic Disparities in California Ambulance Patient Offload Times

Abstract

Importance: Patient demographic and socioeconomic characteristics are associated with differential delays in access to emergency care. However, less is known about the association between demographic, socioeconomic, and emergency medical services (EMS) agency factors and ambulance patient offload times (APOT), a critical measure of timely access to emergency care.

Objective: To determine the association between ambulance offload times and demographic, socioeconomic, and EMS agency factors, uncover disparities in offload delays, and investigate factors associated with long APOT.

Design, setting, and participants: This retrospective cohort study was conducted using offload data from the California EMS Authority and local EMS agencies (LEMSA), population data from the US Census Bureau, and demographic and socioeconomic data from the Centers for Disease Control and Prevention's Social Vulnerability Index. California local EMS agencies participated from January 1, 2021, to June 30, 2023.

Exposure: A total of 30 community demographic, socioeconomic, and LEMSA factors were assessed.

Main outcomes and measures: The main outcome was weighted mean APOT, calculated from APOT measures obtained from the California Emergency Medical Services Authroity and LEMSAs. The association between APOT and area demographic and socioeconomic characteristics was assessed using linear regression.

Results: In this retrospective study from January 1, 2021, to June 30, 2023, 5 913 399 offloads were observed across 34 California LEMSAs with median (IQR) of 0.3% (0.2%-0.4%) American Indian or Alaska Native residents, 7.1% (4.7%-1.5%) Asian residents, 2.2% (1.6%-4.9%) Black residents, 33.1% (22.5%-48.7%) Hispanic or Latino residents, 0.3% (0.2%-0.4%) Native Hawaiian or Pacific Islander residents, 4.1% (3.1%-4.9%) multiracial, and 0.4% (0.4%-0.5%) residents in the additional race category; 17.2% (14.7%-22.8%) residents living below 150% of the poverty line; and 15.7% (13.5%-20.1%) aged 65 years or older. The weighted mean (SD) APOT across California was 42.8 (27.3) minutes; the median (IQR) across LEMSAs was 27.0 (15.5-48.3) minutes. Sequential unadjusted linear regressions of the 30 characteristics revealed 11 that were significantly associated with APOT. Least absolute shrinkage and selection operator penalization identified Black race, being aged 65 years or older, and total offloads (all log-transformed) as the variables most associated with APOT. A 3.3% absolute increase in Black residents, from 1.6% (25th percentile) to 4.9% (75th percentile), was associated with an unadjusted 17.4-minute (95% CI 10.3-24.5) increase in APOT. This increase remained significant, at 11.75 (95% CI 1.9-21.6) minutes, after adjustments for demographic, socioeconomic, and LEMSA characteristics.

Conclusions and relevance: This cohort study of 5.9 million ambulance offloads found that the proportion of Black residents was the factor most significantly associated with longer APOT. These findings have direct implications for patients, EMS systems, and hospitals, as APOT may be an important component of health disparities in emergency care.

Figure 1.. Estimated Ambulance Patient Offload Time (APOT) Change (Minutes) Associated With a Black Race Population Fraction Increase From the 25th to 75th Percentiles Observed in CA Local Emergency Medical Services Agencies (LEMSA)

Figure 1 has been adjusted for suspected confounders at marginal mean levels: remaining race categories, single-parent households, 150% poverty, age categories, LEMSA characteristics, and socioeconomic variables. ^aRemaining race categories: population fraction that is Hispanic or Latino, Asian (not Hispanic or Latino), American Indian or Alaska Native (not Hispanic or Latino), Native Hawaiian or Pacific Islander (not Hispanic or Latino), or additional races (not Hispanic or Latino). ^bAdjusted for both 150% poverty and its interaction with Black race proportion. ^cAge categories: population fraction that is aged 65 years and older or 17 years and younger. ^dSocioeconomic variables: population proportion that is unemployed, burdened by housing cost, has limited English proficiency, has no health insurance, has no High School diploma, and has no vehicle. ^eLEMSA characteristics: population, number of offloads, and area (square miles).

Figure 2.. Adjusted Association Between Black Resident Proportion and Ambulance Patient Offload Time (APOT)

The association between APOT (minutes) and percentage Black race, estimated from the model fully adjusted for remaining race and age categories, single parent households, all available socioeconomic and LEMSA characteristics, and the interaction between Black race and economic disadvantage.

Figure 3.. Estimated Association of Black Race Proportion and Ambulance Patient Offload Time (APOT), Adjusted for Local Emergency Medical Services Agency (LEMSA) Population, Offloads, and Area, at the 25th and 75th Percentiles of Residents Living Below 150% Poverty

Estimated associations between the proportion of residents reporting Black race and APOT for the 75th percentile of economic disadvantage (blue) and then 25th percentile of economic disadvantage (orange) of observed LEMSAs, adjusted for LEMSA population, offloads, and area.