Boarding admitted patients in the emergency department due to high hospital occupancy is a worldwide problem. However, whether or not emergency department-boarded patients managed by emergency department providers subjects them to increased serious complications needs further clarification.

A multivariate logistic regression analysis was used to examine the relationship of patient's age, sex, arrival hours, diagnostic category, triage category, daily emergency department visits, and daily hospital occupancy to the occurrence of serious complications within 24 hours for 20,276 emergency admissions in a 4-year period.

A vast majority of study days (86.5%) saw very high occupancy ≥90%. Serious complications incidence was 13.62 per 1000 patient days when hospital occupancy was ≤90%, and it increased significantly to 17.10 and 22.52 per 1000 patient days for occupancy at 90%-95% and ≥95%, respectively. In the multivariate analysis, significant risk factors for serious complications included daily occupancy ≥95% (adjusted odds ratio [OR] 1.73; 95% confidence interval [CI], 1.26-2.39), triage category (adjusted OR 0.20; 95% CI, 0.17-0.24), and specific diagnoses (injury and poisoning [adjusted OR 1.62; 95% CI, 1.22-2.84], respiratory [adjusted OR 2.48; 95% CI, 1.37-4.49], and circulatory [adjusted OR 3.24; 95% CI, 1.80-5.80]).

High hospital occupancy was associated with an increased incidence of serious complications within 24 hours for patients admitted but still boarded in the emergency department and managed by emergency department providers.