National trends in emergency department occupancy, 2001 to 2008: effect of inpatient admissions versus emergency department practice intensity

Study objective: We evaluate recent trends in emergency department (ED) crowding and its potential causes by analyzing ED occupancy, a proxy measure for ED crowding.

Methods: We analyzed data from the annual National Hospital Ambulatory Medical Care Surveys from 2001 to 2008. The surveys abstract patient records from a national sample of hospital EDs to generate nationally representative estimates of visits. We used time of ED arrival and length of ED visit to calculate mean and hourly ED occupancy.

Results: During the 8-year study period, the number of ED visits increased by 1.9% per year (95% confidence interval 1.2% to 2.5%), a rate 60% faster than population growth. Mean occupancy increased even more rapidly, at 3.1% per year (95% confidence interval 2.3% to 3.8%), or 27% during the 8 study years. Among potential factors associated with crowding, the use of advanced imaging increased most, by 140%. But advanced imaging had a smaller effect on the occupancy trend than other more common throughput factors, such as the use of intravenous fluids and blood tests, the performance of any clinical procedure, and the mention of 2 or more medications. Of patient characteristics, Medicare payer status and the age group 45 to 64 years accounted for small disproportionate increases in occupancy.

Conclusion: Despite repeated calls for action, ED crowding is getting worse. Sociodemographic changes account for some of the increase, but practice intensity is the principal factor driving increasing occupancy levels. Although hospital admission generated longer ED stays than any other factor, it did not influence the steep trend in occupancy.