University of Iowa News Release
July 23, 2004
Risk Of Death Not Significantly Higher For Patients Admitted On Weekends
Hospital staffing levels are typically lower on weekends compared to weekdays, and some studies have suggested that the risk of mortality (death) for patients admitted on weekends is much higher than for patients admitted on weekdays.
However, patients admitted on weekends do not have a significantly higher risk of mortality than those admitted on weekdays, according to a University of Iowa-led study that appears in the Aug. 1 issue of the American Journal of Medicine.
The UI team analyzed administrative records from 1998 for 641,860 patients admitted to 441 hospitals in California. Of those patients, all of whom were admitted through emergency departments, there were 41,701 deaths. The researchers found only a three percent greater likelihood of death among patients admitted on weekends compared with patients admitted on weekdays -- the "weekend effect."
Prior studies have reported the "weekend effect" risk to be 10 percent or higher. However, the UI researchers said these prior investigations did not appear to compare similar groups of patients, which could create bias. The UI study used different methodological approaches to eliminate the possibility of bias.
"We found that patients admitted to hospitals on weekends experience a very minimally increased mortality compared to patients admitted on weekdays. This should reassure both patients and providers," said Peter Cram, M.D., M.B.A., the study's lead author and assistant professor of internal medicine in the UI Roy J. and Lucille A. Carver College of Medicine.
"Prior studies showed that patients admitted on weekends may be more likely to die when compared with patients admitted on weekdays, but in these studies, the patients admitted on weekends were probably sicker in ways that the prior studies did not recognize, and as a result, were at increased risk of dying. In our study, we looked very specifically at patient populations that were nearly identical," he added.
The results support an earlier investigation that was led by Gary Rosenthal, M.D., another author on the current study, UI professor of internal medicine and director of the UI Division of General Internal Medicine. In the June 2002 issue of the journal Medical Care, Rosenthal's team showed little weekend effect related to intensive care unit admissions.
In the current study, the three percent difference in mortality provides insight into the implications that different ways of organizing health care delivery have on patient outcomes, said Rosenthal, who also is a staff physician and researcher with the Veterans Affairs (VA) Iowa City Health Care System, where he directs the Center for Research in the Implementation of Innovative Strategies in Practice.
"It is somewhat comforting that we didn't see any significant adverse effects of decreased staffing in hospitals. The results suggest that even though service levels may differ on the weekend compared to the weekday, there are adequate mechanisms in place to ensure patient safety," Rosenthal explained.
The new study also indicated that major teaching hospitals show more variation between weekend-admission and weekday-admission death rates, compared to the weekend and weekday death rate difference at other hospitals.
The finding was somewhat surprising, the researchers said, given that patients admitted to teaching hospitals have lower death rates overall than patients admitted to non-teaching hospitals.
"While major teaching hospitals have lower death rates overall, we saw some evidence that they may have greater variation between their weekend-admission and week-day admission mortality rates than other hospitals," Cram said.
However, both he and Rosenthal noted that this specific finding needs confirmation.
"It is possible that there are unique selection factors involving admission to teaching hospitals on weekends and that our method of adjusting for severity and illness and risk did not account for these," Rosenthal said.
In addition, to Cram and Rosenthal, the UI team include Mitchell Barnett, health services research specialist with the VA Iowa City Health Care System and a doctoral student in the UI College of Pharmacy, and Stephen Hillis, Ph.D., a data analyst with the VA in Iowa City.
The study was supported in part by a Research Enhancement Award from the U.S. Department of Veterans Affairs. Rosenthal is a senior quality scholar with the Veterans Health Administration.
Information about the June 2002 study is available online at http://news-releases.uiowa.edu/2002/september/0905weekend-effect.html.
University of Iowa Health Care describes the partnership between the UI Roy J. and Lucille A. Carver College of Medicine and UI Hospitals and Clinics and the patient care, medical education and research programs and services they provide. Visit UI Health Care online at http://www.uihealthcare.com.
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