Overcrowding at emergency departments is a serious patient-safety issue and must be made a public health priority, conclude the authors of a study published this week in the Annals of Emergency Medicine.

Patients at overcrowded emergency departments were 5% more likely to die as compared with patients cared for at less-crowded EDs, according to the study's researchers. The researchers measured overcrowding using ambulance diversion—the practice of hospitals closing emergency rooms to ambulances because they are too busy to accept new patients.

The increased probability of death arose from EDs with median high ambulance diversions of seven hours compared with a median low of zero. The data came from 995,379 ED visits in 2007 at 187 non-federal, acute-care hospitals in California. Overcrowding was linked to 300 inpatient deaths.

"Our findings support the perception of ED crowding as a marker of poor quality of care," the authors wrote (PDF). The Annals of Emergency Medicine is the journal of the American College of Emergency Physicians.

"Despite mounting evidence that ED crowding is a health-delivery problem that reduces access to emergency care, results in worse quality of care and leads to lower patient satisfaction, there have subsequently been few systematic actions to address the crisis of ED crowding," the authors concluded. "Policymakers should heed the recommendations of the Institute of Medicine and address ED crowding as an important public health priority."

The study referred to a 2006 IOM report (PDF), "Future of Emergency Care: Hospital-Based Emergency Care at the Breaking Point," that warned of an overburdened emergency-care system.

"Emergency department crowding is likely to become worse in the future because of the volume, complexity and acuity of emergency patients," the study's lead author, Dr. Benjamin Sun of Oregon Health & Science University in Portland, said in a news release. "Policymakers should address ER crowding as an important public health priority."