Trainee doctors have double the risk of having a car crash when they work more than 24 consecutive hours, according to a new report.

“Scheduling physicians to work such extended shifts ... poses a serious and preventable safety hazard for them and other motorists,” Dr. Charles A. Czeisler, from Harvard Medical School in Boston, and colleagues note in this week’s New England Journal of Medicine.

At present, however, the Accreditation Council for Graduate Medical Education guidelines still allow interns to work up to 30 consecutive hours every other shift, the investigators point out.

The new findings are based on a survey of 2737 interns who completed monthly reports detailing their work hours, motor vehicle crashes, and near-miss incidents. An extended work shift was defined as at least 24 consecutive hours.

Working an extended shift raised the risk of crashes and near-miss incidents by 2.3- and 5.9-fold, respectively.

Moreover, for each extended shift scheduled during a month, the risk of any crashes increased by 9.1 percent, and crashes during the commute from work rose by 16.2 percent.

Months with five or more extended shifts more than doubled the risk that the intern would fall asleep while operating a motor vehicle, the team reports.

In a related editorial, C. Dennis Wylie, a motor vehicle crash expert from Santa Barbara, California, comments: “I believe the heightened (crash) risk associated with extended works shifts that has been identified (in this study) is convincing scientific evidence of the need to improve the enforcement of the hours-of-service policy.”

SOURCE: New England Journal of Medicine, January 13, 2005.