The Importance of Neighborhood in 9-1-1 Ambulance Contacts: A Geospatial Analysis of Medical and Trauma Emergencies in Denver

Background: Prehospital emergency care is a vital component of healthcare access, and emergency medical services (EMS) plays an essential role in healthcare delivery. Understanding the distribution of medical and trauma EMS calls at the neighborhood level would be beneficial to identify at-risk communities and facilitate targeted interventions. Objectives: The primary objective was to evaluate and characterize 9-1-1 ambulance contacts for medical and trauma-related events in Denver. The secondary objective was to evaluate the co-existence of medical and trauma-related EMS calls to determine if these emergencies occur in the same neighborhoods. Methods: We conducted a secondary analysis of prospectively collected EMS calls in Denver between January 1, 2011, through August 8, 2017. The primary outcome was the incidence of trauma and medical EMS calls in each census tract. EMS events were aggregated to tracts and incidence rates were calculated based on the adult daytime and nighttime population. Three different spatial analysis methods (SaTScan's spatial scan statistic, Gini coefficient, and Local Moran's I) were utilized to identify clusters of medical and trauma EMS events at the tract level. Results: A total of 425,527 EMS calls in 142 census tracts occurred during the study period. The median age of study participants was 48 (IQR 33, 62), 56% were male, and the majority (74%) of EMS calls were for medical events. An emergent EMS return to the hospital occurred in 5% of all calls. We identified several high-risk census tracts with a coexistence of medical and trauma EMS events. When compared to the Denver County population, the tracts with high EMS call rates were diverse, with many tracts exhibiting a higher proportion of black, unemployment, below poverty, and lower median income while other tracts demonstrated a smaller proportion of black, unemployment, below poverty, and a higher median income. Conclusions: Disparities exist in the distribution of medical and trauma EMS calls in varied census tracts in Denver. Identifying neighborhoods in which there is an incidence of higher medical and trauma emergencies is important to guide EMS care delivery and may help facilitate targeted public health interventions for at-risk populations to improve health outcomes.