• overcrowding;
  • emergency health services;
  • hospital services;
  • utilization;
  • time series analysis


Emergency department (ED) overcrowding is a common problem. Despite a widespread belief that low hospital bed availability contributes to ED overcrowding, there are few data demonstrating this effect. Objectives: To identify the effect of hospital occupancy on ED length of stay for admitted patients and patient disposition. Methods: This was an observational study design using administrative data at a 500-bed acute care teaching hospital. All patients presenting to the ED between April 1993 and June 1999 were included in the study. The predictor variable was daily hospital occupancy. Outcome measures included daily ED length of stay for admitted patients, daily consultation rate, and daily admission rate. The models controlled for the average daily age of ED patients and the average daily “arrival density” index, which adjusts for patient volume and clustering of patient arrivals. Results: The average hospital occupancy was 89.7%. On average 155 patients visited the ED daily; 21% were referred to hospital physicians and 19% were admitted. The median ED length of stay for admitted patients was 5 hours 54 minutes (interquartile range 5 hr 12 min to 6 hr 42 min). Daily ED length of stay for admitted patients increased 18 minutes (95% CI = 12 to 24) when there was an absolute increase in occupancy of 10%. The ED length of stay appeared to increase extensively when hospital occupancy exceeded a threshold of 90%. Consultation and admission rates were not influenced by hospital occupancy. Conclusions: Increased hospital occupancy is strongly associated with ED length of stay for admitted patients. Increasing hospital bed availability might reduce ED overcrowding.