Intended for healthcare professionals


Overcrowding in emergency departments and adverse outcomes

BMJ 2011; 342 doi: (Published 01 June 2011) Cite this as: BMJ 2011;342:d2830
  1. Melissa L McCarthy, associate professor
  1. 1Departments of Health Policy and Emergency Medicine, George Washington University, Washington, DC 20037, USA
  1. melissa.mccarthy{at}

Death and admission rates are higher when length of stay is longer

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 who present during shifts with long waiting times are at risk for adverse events. The authors found that as the average shift length of stay of all patients treated in the emergency department increased, a corresponding increase occurred in the risk of death or hospital admission within seven days of the visit in patients who were treated and released or who left without being seen.8

The study’s findings are remarkable in several ways. Firstly, the study focused on patients discharged from the emergency department (those who were treated and released or left without being seen), so the higher mortality and rates of hospital admission are not confounded by variability in inpatient care. Secondly, because the authors compared short term adverse events within each emergency department, they eliminated confounding by site to site variability across the 125 emergency departments in their sample (such as differences in illness severity or resources available). The authors compared patients treated at the same emergency department and found that short term risk of death or hospital admission increased with longer length of stay. Finally, this is the first population based cohort study to show that patients who leave without being seen are not at higher risk of short term death or hospital admission than those treated and released from the emergency department.

The results of this study may come as a surprise to many people, including emergency department clinicians. Why? Because rarely do we know the outcomes of patients who visit the emergency department. Most emergency departments do not routinely track patient outcomes, except for patient satisfaction, recidivism, and rates of leaving without being seen. We need to extend the evaluation of emergency care to either the resolution of the problem or transfer of care to a provider better suited to tackle the patient’s needs. The quality of emergency care could be greatly improved if the health and wellbeing of patients were tracked after they left the emergency department. A more rigorous and comprehensive focus on patient outcomes would result in better integration of emergency medicine into the patient care pathway.

The study begs the question of why overcrowding is associated with a higher risk of short term mortality and hospital admission in patients who complete care in the emergency department. Does overcrowding cause cognitive overload that impairs clinicians’ judgment? Do clinicians alter their treatment decisions because of overcrowding? When treatment takes longer, patients are likely to be cared for by more providers; does this negatively affect delivery of care and put patients at increased risk of adverse events? How can we use technology to mitigate the negative effects of overcrowding on patient care and outcomes?

What needs to happen next to improve practice? The results make a compelling case for the need to improve the operational efficiency of emergency departments. Length of stay is an efficiency measure9; the study shows that when emergency departments operate less efficiently, more deaths and hospital admissions occur in discharged patients. Emergency departments must be redesigned to meet patients’ needs more effectively and efficiently. This includes having information systems that readily provide operational (such as patient cycle times) and clinical (such as vital signs, diagnostic test results, care plans, etc) information to clinicians to support their decision making and to allow information to flow easily between settings in a timely fashion. Better integration of information and technology into the emergency department work flow will make care processes more timely, efficient, and reliable. Ongoing measurement of patient outcomes is essential so that emergency departments continuously analyse and improve their performance. Finally, seamless integration between the emergency department and hospital and a stronger linkage to ambulatory care providers are needed to enhance delivery of care and clinical effectiveness.


Cite this as: BMJ 2011;342:d2830


  • Research, doi:10.1136/bmj.d2983
  • Competing interests: The author has completed the Unified Competing Interest form at (available on request from the corresponding author) and declares: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.

  • Provenance and peer review: Commissioned; not externally peer reviewed.


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