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Medical interns who work extended-duration shifts double their risk of car crashes when driving home from the hospital

Drowsy driving is a well-known hazard that causes more than 100,000 motor vehicle crashes on the Nation's highways every year. According to a recent study, first-year doctors in training, or medical interns, who work shifts of longer than 24 hours are more than twice as likely to have a car crash leaving the hospital and five times as likely to have a "near miss" incident on the road as medical interns who work shorter shifts. The study was supported by the Agency for Healthcare Research and Quality (HS12032 and F32 HS14130) and the National Institute for Occupational Safety and Health (NIOSH) in the Centers for Disease Control and Prevention.

Details of the study were published in an article that appeared in the January 13, 2005, issue of the New England Journal of Medicine. The article is the third in a series of studies cofunded by AHRQ and NIOSH on the impact of extended work hours and fatigue on interns conducted by the Divisions of Sleep Medicine at the Brigham and Women's Hospital and the Harvard Medical School in Boston. The first two studies were published in the October 28, 2004, issue of the same journal. Charles A. Czeisler, Ph.D., M.D., leads the Harvard Work Hours, Health, and Safety Group, the team that conducted all three studies. Dr. Czeisler is Baldino Professor of Sleep Medicine and Director of the Division of Sleep Medicine at Harvard Medical School.

For this study, Laura K. Barger, Ph.D., research associate in medicine at the Brigham and Women's Hospital and Harvard Medical School, and her colleagues recruited 2,737 interns from medical institutions around the country to fill out detailed monthly surveys recording their work hours, frequency of shifts of more than 24 hours, and driving safety records, including car accidents, near-miss incidents in which property damage was narrowly avoided, and incidents in which they had fallen asleep while driving or while stopped in traffic. More than 17,000 surveys were collected between April 2002 and May 2003. Researchers also randomly selected 7 percent of study participants to keep daily work diaries that were verified through direct observation.

The researchers found that the majority of interns routinely worked more than 30 consecutive hours, and the interns reported that on average, they were awake 96 percent of the time they were in the hospital. Also, during the 12-month study period, interns reported working an average of 80 hours or more during 46 percent of work weeks and 100 hours or more per week during 11 percent of work weeks.

Study participants reported a total of 320 accidents during the 12-month study period, including 133 that resulted in treatment in the emergency room, property damage of more than $1,000, or the filing of a police report. Slightly more than 40 percent of the 320 crashes occurred on the commute from work. Every extended shift that was scheduled per month increased the monthly rate of accidents on the commute from work by 16 percent and the monthly rate of any car accident by 9 percent. Interns also were more than twice as likely to fall asleep while driving and more than three times as likely to fall asleep while stopped in traffic in months during which they worked five or more extended shifts.

For more information, see "Extended work shifts and the risk of motor vehicle crashes among interns," by Dr. Barger, Brian E. Cade, M.S., Najib T. Ayas, M.D., M.P.H., and others, in the January 13, 2005, New England Journal of Medicine 352, pp. 125-134.

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