CHICAGO (AP) — Surgery patients fared just as well when junior doctors worked longer than mandated hours in the first major rigorous test of regulations many physicians say hurt medical education.

Nationwide limits on work hours were established more than a decade ago because of concerns that sleep-deprived medical residents were a threat to themselves and their patients. To test that, researchers randomly assigned more than 4,000 surgery residents to regulation hours or a more flexible schedule that allowed them to continue with a case after their shifts ended. That sometimes meant working for more than 28 hours at a time.

The study looked at how many patients died or had serious complications in the month after surgery and found the same low rate — about 9 percent — in both groups. Residents' self-rated dissatisfaction with their education and with their well-being were similarly low — 11 percent and roughly 13 percent respectively in each group.

It's a landmark study, testing "a hot button, controversial issue in health care," said lead author Dr. Karl Bilimoria, director of surgical outcomes and quality improvement at Northwestern University's Feinberg medical school. Without flexibility, rookie doctors often have to end their shifts in the middle of caring for patients, handing them off to another medical resident. That can happen at critical times, disrupting the doctor-patient relationship, Bilimoria said.

"Our hope would be that the evidence would be used ... to change policies fairly soon and allow flexibility back into surgical residency," he said.

Residents' work limits were first set in 2003 by the Accreditation Council for Graduate Medical Education, and revised in 2011. The rules include 80-hour maximum work weeks.

The group said it will consider the results as part of an ongoing review of residents' work hour standards. The council, the American College of Surgeons and the American Board of Surgery paid for the study, which was published Tuesday by the New England Journal of Medicine.

The study involved almost 139,000 patients treated at 151 hospitals nationwide.

A Mayo Clinic neurosurgery resident, Dr. Maya Babu, said the study results were not at all surprising. She's head of an American College of Surgeons' residents group.

Under the limits, Babu said she has sometimes had to clock out at inopportune times, even in the middle of brain tumor operations, missing important learning opportunities.

She said if allowed flexible hours, most residents would know when to speak up and say they're too tired to continue working.

The rules affect medical school graduates involved in residency training programs in hospitals. The rules include shift limits of 16 hours for junior residents and 28 hours for senior residents; 8 to 10 hours off between shifts, but 14 hours off after a 24-hour shift.

Half the residents worked under those limits in the study. The flex-hour group could work longer hours with less time off between shifts, but both groups worked under the 80-hour-per week limit, averaged over four weeks.

Dr. John Birkmeyer, a surgeon and health outcomes policy expert at the Dartmouth-Hitchcock Medical Center, said in a journal editorial that the study "effectively debunks concerns that patients will suffer as a result of increased handoffs and breaks in the continuity of care." But Birkmeyer opposes easing work limits and advocates medical training that doesn't "depend on overworked resident physicians."

Many would love to hear "'we can take care of this case without you. Go home, see your family, and come in fresh tomorrow,'" Birkmeyer said.

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Online:

Journal: http://www.nejm.org

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Follow AP Medical Writer Lindsey Tanner at http://www.twitter.com/LindseyTanner. Her work can be found at http://bigstory.ap.org/content/lindsey-tanner