Medical patient boarding in the emergency department as a source of crowding and delay-related harm, impacting patient outcomes and the efficiency of urgent and emergency care

Background: Previous studies have indicated that crowding within the emergency department (ED) is associated with longer lengths of stay in the ED and higher mortality. Boarding, the time patients spend waiting for an inpatient bed after ED assessment, represents a clinically unproductive delay and occupies scarce ED resources. We explore the association of medical patient boarding not only with their outcomes but also indirectly for other patients in the ED and those in and awaiting ambulances. Methods: A retrospective cohort study using routine data for 3 EDs in England from July 2023 to May 2025 was performed. Direct, delay-related harm outcomes of medical patient boarding time were investigated: inpatient length of stay and 30-day re-admission and mortality rates. Indirect, crowding-mediated outcomes of medical patient boarding levels consisted of time in ED for non-admitted patients, ambulance handover times and Category 1, Category 2 and Category 3 ambulance response times. Mixed-effects regression analysis modelled each relationship while controlling for potential confounding. Results: The study examined 49 034 medical admissions, 210 334 non-admitted ED patients, 88 633 ambulance handovers and 146 278 ambulance responses. Medical patients, accounting for two-thirds of ED admissions, constituted 81% of total ED boarding time. Regression analysis showed that for a typical 25-bed ED, each additional five medical boarders was associated with an extra 7.9 min and 51.9 min ambulance response times for Category 2 and Category 3 calls and an extra 9.9 min of extra ambulance handover time. For admitted medical patients, each additional 4 hours of boarding time was associated with an extra 8.6 hours of inpatient length of stay and an 8.4% increase in the odds of 30-day mortality. Conclusion: Boarding medical patients in the ED is associated with a significant increase in their risk of harm, including higher mortality and longer hospital stays. It also adversely affects other patients by delaying ambulances and reducing overall bed availability through extended inpatient stays.