Overcrowding in emergency departments and adverse outcomes

Crowded emergency departments are a problem for healthcare systems in many countries.1 2 3 Numerous studies have documented poorer quality of care and more patient dissatisfaction in these circumstances,4 5 but few have examined the effect of crowding on patient mortality and morbidity.6 7 One study reported 34% higher short term mortality in patients arriving during crowded periods compared with those arriving during non-crowded periods, but the study was performed at a single site and limited to in-hospital deaths.6 Another study reported higher mortality at two, seven, and 30 days after the visit for patients who arrived during high hospital occupancy or long periods of stay in the emergency department. However, this study included only patients admitted to hospital from the emergency department and did not estimate the independent effects of hospital occupancy versus long stay in the emergency department on mortality.7

In the linked population cohort study (doi:10.1136/bmj.d2983) Guttmann and colleagues assessed whether non-admitted patients …