But the results published in the Annals of Surgery found the trainee doctors didn't actually get any more sleep under the limited work hours policy, and also said they felt less prepared as doctors and were less satisfied with their education.

In July 2003, the U.S. Accreditation Council for Graduate Medical Education implemented new policy limiting the on-duty hours of notoriously sleep-deprived residents to 80 per week, with a minimum of ten hours off between shifts. Those changes were further updated in 2011.

The main goal was to ease young doctors' fatigue and fatigue-related medical errors.

The work limits seem to have been somewhat successful, but they also come at a cost, according to Debra Weinstein from Massachusetts General Hospital and Brigham and Women's Hospital in Boston, who worked on the study.

"The extent to which we restrict residents' time in the hospital does risk (affecting) their skill and sense of preparedness," she said.

"Continuing to further limit duty hours may not be the best way to address the goals of patient safety, resident well-being and excellent medical education."

Some past studies have suggested that work limits improve quality of life for residents, but have a negative impact on their education. One survey published last year found that the majority of surgery residents worked more hours than the current regulations allowed.

In the new study, researchers analyzed surveys completed by a total of 216 residents at the Harvard Orthopedic Combined Residency Program between 2003 and 2009.

Compared to pre-2003 residents, orthopedic trainees in 2009 reported working fewer hours per week, about 66 hours versus 75. But they didn't get any more sleep. Throughout the study period, they reported sleeping for about five hours every night, on average.

Residents rated their own preparedness to make clinical decisions under stress and their ability to perform the range of skills expected of them slightly lower in later years, the researchers said.

After the work-hour policies went into place, residents did say they spent fewer days feeling very tired, and a smaller proportion of them said their fatigue had a negative impact on patient care and safety.

Forty-six percent of residents said their fatigue affected the quality of care they provided in 2003, compared to 26 percent on the 2004 through 2009 surveys.

"There's a general assumption that reducing work hours will result in more sleep for tired residents, and clearly out findings challenge that," Weinstein said.

However, it's possible that having more time to decompress and relieve psychological stress may improve residents' sense of well-being, even if they're not getting more sleep, she added.

Weinstein and her colleagues noted that their study didn't include objective measures of residents' performance, so they couldn't tell whether they actually did better or worse on exams, or made more or fewer errors. SOURCE: bit.ly/TcFx66

(Reporting by Elaine Lies)

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