Long shifts and little sleep may make medical interns (search) dangerous drivers, a new study shows.

Researchers found that residents in their first year of training after medical school, known as interns, were more than twice as likely to report a traffic accident after working long hours than after working a normal shift. In addition, interns were nearly six times as likely to report a near-miss incident after an extended shift because they fell asleep at the wheel.

Despite long-standing concerns about the effects of working extended shifts of more than 24 hours on the performance of medical residents, researchers say these long hours remain a hallmark of medical education in the U.S. But few studies have looked at a specific result of the intern’s work schedule, such as traffic accidents or falling asleep at the wheel.

The findings indicate that scheduling interns to work such extended shifts not only increases the risk of serious medical errors (search), but “poses a serious and preventable safety hazard for them and other motorists,” write Laura K. Barger, PhD, of the Channing Laboratory of Harvard Medical School, and colleagues.

“These results have important implications for scheduling practices in medical-residency programs,” they write in this week’s issue of The New England Journal of Medicine.

Beware of Medical Residents on the Road

In the study, researchers surveyed 2,737 residents in their first year after medical school and asked them about their work schedules and any documented traffic accidents or near-miss incidents involving them falling asleep at the wheel.

Researchers found the medical residents worked an average of about four extended shifts per month with an average duration of about 32 hours.

The analysis showed that for every extended shift that was scheduled in a month, the monthly risk of a traffic accident increased by 9 percent, and the monthly risk of a crash during the commute from work rose by 16 percent.

In the months that medical residents worked five or more extended shifts, the risk that they would fall asleep at the wheel while driving or while stopped in traffic more than doubled and tripled, respectively.

Researchers say these findings are of particular concern because motor vehicle accidents are the leading cause of death among young adults.

“Given the number of interns in our study who commuted by car (69 percent), these data suggest that implementation of a work schedule for interns without any extended shifts could prevent a substantial number of crashes,” write the researchers.

By Jennifer Warner, reviewed by Brunilda Nazario, MD

SOURCE: Barger, L. The New England Journal of Medicine, Jan. 13, 2005; vol 352: pp 125-34.