Admission-time-dependent variation in mortality in a Danish emergency department

Introduction: The inflow of patients in emergency departments (ED) varies over time. If variations are not anticipated, accumulation of patients and treatment delay may occur. This may trigger adverse events causing excess mortality. The aim of this study was to determine if attending the ED after hours and during weekends was associated with an increased mortality. Methods: We examined the medical records of 5,385 patients. Data were retrieved from the Electronic Patient Journal, the Danish National Patient Registry and the Danish Civil Registration System. Multinomial logistic regression and Cox regression were performed to analyse the associations between attendance time and mortality. Results: The inflow of patients differed over the hours of the day and the days of the week. The findings tended towards a higher mortality for patients attending the ED during the evening shift than during the dayshifts, and during weekends than during weekdays. Patients attending the ED during the night shift had no excess mortality compared with the dayshifts. The combination of evening shift and weekday and the combination of dayshift and weekend reached significance. Associations with mortality were strongest for in-hospital mortality. Conclusions: Indications of excess mortality were found for patients attending in the weekend compared with weekdays and in the evening hours compared with night and daytime hours. The causal mechanism is unknown.