With an ominous warning in the background, Charles Czeisler and Laura Barger review data that show the sometimes deadly result of interns driving home after working heroic shifts of 30 or more continuous hours. (Staff photo Jon Chase/Harvard News Office)

How well do you think you could drive home after working continuously for 30 hours as part of an 80-hour per week routine?

Medical interns do this all the time. If that makes you think such caregivers could get involved in a worrisome number of medical errors as well as get into more car accidents than your average 9-to-5 workers, you would be right.

A safety group at Harvard University has looked into the behavior of those in training in hospitals and found that overworked interns made 36 percent more serious medical errors and five times as many diagnostic mistakes during a traditional work shift than their better rested colleagues.

More recently, the safety researchers checked interns' driving habits and found that their odds of crashing more than double as work hours increase. The doctors-in-training also experienced more than five times as many near misses as nonsleep-deprived drivers.

"These findings are of particular concern because motor vehicle crashes are the leading cause of death in this age group," notes Charles Czeisler, Baldino Professor of Sleep Medicine at Harvard Medical School. Interns, men and women in their first year of residency at teaching hospitals, usually are between 24 and 32 years old.

Czeisler and other members of the Harvard Work Hours, Health and Safety Group followed the work/sleep/driving habits of 2,737 interns in hospitals nationwide from July 2002 until May 2003. They used monthly Web site questionnaires, police reports, and other documentation.

"Extrapolation of the results to the wider population of 102,577 person-years worked by residents in U.S. hospitals in 2002-2003, suggests that physicians in training worked approximately 20,000 extended shifts that exceeded 40 consecutive hours," notes Laura Barger, a research fellow and lead author of the study report. "Our data suggests that 10 percent of these shifts may have exceeded 64 continuous hours." The report appears in the Jan. 13 issue of the New England Journal of Medicine.

Lethal matters

Since that research was completed, duty hours for interns and other residents have been limited to 80 hours per week by the Accreditation Council for Graduate Medical Education. However, the new standard still allows people to work for continuous stretches of 30 hours.

"Interns often work two 30-hour shifts in one week," Czeisler observes. Other research has found that a single sleepless night impairs performance to a level similar to a blood alcohol level of 0.1 percent, enough to get you arrested for drunk driving in most states. "It's unsafe to get behind the wheel after working 24 consecutive hours," Czeisler points out. "The health-care profession has a duty to protect its young trainees from exposure to the well-known hazards of drowsy driving, which causes more than 100,000 motor vehicle crashes on U.S. highways every year."

Working in the Division of Sleep Medicine at Harvard Medical School, Czeisler has been interested in the problem of driving accidents caused by lack of sleep for 10 years. "You hear so many stories about tragic results," he notes. In one case, a resident died in an emergency room after a car crash. In another, a young doctor and father of three died when he fell asleep while driving home from the hospital after working all weekend.

In 2001, Czeisler applied for and received a grant from the National Institute of Occupational Safety and Health to do a large study of the subject. He and several colleagues sent thousands of e-mails to those on a national list of residents, asking them to participate in "an exciting survey of work hours and health." To motivate them, the researchers offered various awards from $100 to $1,000 to those who completed 12 monthly Internet questionnaires. Prize-winners were later chosen by lottery.

Questions about extended work shifts and car crashes were distributed among others about health and safety, so participants did not know the exact purpose of the survey.

"We found the odds that interns will have a documented motor vehicle crash on their commute after an extended work shift [24 hours or more] were more than double the odds after a nonextended shift," the report states. "Near-miss incidents were more than five times as likely to occur. Given the percentage of interns 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."

Legal matters

The report points out that, in addition to the increased risks for injury and deaths, such accident have legal implications. Drivers in the United States and Great Britain have been convicted of vehicular homicide for driving while impaired by sleepiness. In New Jersey, a vehicular homicide law now includes in its definition of reckless driving "driving after having been without sleep for a period in excess of 24 consecutive hours." Similar legislation is pending in Massachusetts, New York, and Michigan.

Czeisler describes an Illinois court case involving a medical intern who fell asleep while driving. He hit another car, causing permanent brain damage to a woman who was then a student at Eastern Illinois University. She now has been declared legally incompetent and her parental guardian is suing the hospital where the intern worked.

This is not an isolated situation. Appeals courts in two states have already ruled that an employer's responsibility for fatigue-related fatal crashes continues after an employee leaves work. That's identical to the premise that businesses that serve alcoholic drinks can be held liable for customers who are subsequently involved in alcohol-related car crashes.

"No group is invulnerable to the dangers of driving when deprived of sleep," says Czeisler, "not truckers, nurses, physicians, or surgeons." That fact should provide motivation for acting upon his recommendation that scheduling practices in medical training programs should be changed.

Related stories:

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Lighter schedules reduce serious errors 36 percent