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Association between waiting times and short term mortality and hospital admission after departure from emergency department: population based cohort study from Ontario, Canada

BMJ 2011; 342 doi: (Published 01 June 2011) Cite this as: BMJ 2011;342:d2983
  1. Astrid Guttmann, senior scientist1234,
  2. Michael J Schull, senior scientist and 2010-11 Commonwealth Fund Harkness fellow14567,
  3. Marian J Vermeulen, epidemiologist16,
  4. Therese A Stukel, senior scientist146
  1. 1Institute for Clinical Evaluative Sciences, Toronto, ON, Canada
  2. 2Divisions of Paediatric and Emergency Medicine, Hospital for Sick Children, Toronto
  3. 3Department of Paediatrics, University of Toronto, Toronto
  4. 4Department of Health Policy, Management and Evaluation, University of Toronto, Toronto
  5. 5Department of Emergency Services, Sunnybrook Health Sciences Centre, Toronto
  6. 6Clinical Epidemiology Unit, Sunnybrook Health Sciences Centre, Toronto
  7. 7Department of Medicine, University of Toronto, Toronto
  1. Correspondence to: A Guttmann, Institute for Clinical Evaluative Sciences, G-106, 2075 Bayview Ave, Toronto, ON, Canada M4N 3M5 astrid.guttmann{at}
  • Accepted 28 March 2011


Objective To determine whether patients who are not admitted to hospital after attending an emergency department during shifts with long waiting times are at risk for adverse events.

Design Population based retrospective cohort study using health administrative databases.

Setting High volume emergency departments in Ontario, Canada, fiscal years 2003-7.

Participants All emergency department patients who were not admitted (seen and discharged; left without being seen).

Outcome measures Risk of adverse events (admission to hospital or death within seven days) adjusted for important characteristics of patients, shift, and hospital.

Results 13 934 542 patients were seen and discharged and 617 011 left without being seen. The risk of adverse events increased with the mean length of stay of similar patients in the same shift in the emergency department. For mean length of stay ≥6 v <1 hour the adjusted odds ratio (95% confidence interval) was 1.79 (1.24 to 2.59) for death and 1.95 (1.79 to 2.13) for admission in high acuity patients and 1.71 (1.25 to 2.35) for death and 1.66 (1.56 to 1.76) for admission in low acuity patients). Leaving without being seen was not associated with an increase in adverse events at the level of the patient or by annual rates of the hospital.

Conclusions Presenting to an emergency department during shifts with longer waiting times, reflected in longer mean length of stay, is associated with a greater risk in the short term of death and admission to hospital in patients who are well enough to leave the department. Patients who leave without being seen are not at higher risk of short term adverse events.


  • We thank Kinwah Fung for help with the data analysis and Joel Ray for help in preparing the manuscript.

  • Contributors: AG was responsible for conception, design, analysis, funding, interpretation, drafting of article, and critical revision. MS and TS were involved in design, analysis, interpretation, and critical revision. MV was responsible for design, analysis, interpretation, drafting of article, and critical revision. AG is guarantor. All authors had full access to the data and take responsibility for its integrity and the accuracy of the analysis.

  • Funding: This study was supported by a grant from the Ontario Ministry of Health and Long Term Care and by the Institute for Clinical Evaluative Sciences, which is funded by an annual grant from the Ministry of Health and Long Term Care. The funding source had no involvement in the study design, analysis, interpretation or decision to submit this work.

  • Competing interests: All authors have completed the Unified Competing Interest form at (available on request from the corresponding author) and declare: AG received financial support from the Ontario Ministry of Health and Long Term Care for the submitted work and she and MS receive salary support from the Canadian Institute for Health Research; the authors have no financial relationships with any organizations that might have an interest in the submitted work in the previous 3 years; no other relationships or activities that could appear to have influenced the submitted work.

  • Ethical approval: This study was approved by the research ethics board of Sunnybrook Health Sciences Centre.

  • Data sharing: The technical appendix, dataset creation plan/protocol and statistical code are available from the corresponding author at astrid.guttmann{at}

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