Significant changes in emergency department length of stay and case mix over eight years at a large Swedish University Hospital.

•A change in case mix occurred, primarily with an increase in unstable patients.•Median for all crowding variables, except LOS, were stable over the study period.•Median LOS increased by an average of 9 min/visit/year.•Median LOS increased most among patient groups ≥ 80 years, unstable and admitted.•ED crowding seemed to high extent be related to lack of in-hospital beds.