Strictly limiting the number of hours surgical residents can work has not improved patient outcomes but may have increased complications for some patients and led to higher failure rates on certification exams, a research paper concludes.

Traditionally, doctors in the residency phase of their training spent very long hours in a hospital -- often around-the-clock -- so they could see a wide variety and high volume of patients. In the last 10 years, health authorities started limiting those hours in the hopes of improving patient safety and the education and well-being of doctors.

In 2003, the Accreditation Council for Graduate Medical Education in the United States limited residents' hours to 80 per week. In 2011, the council prohibited first-year residents from working 24 shifts.

In Canada, on-call shifts were limited to 16 hours in Quebec after a provincial arbitrator ruled that in 2011 that a 24-hour on-call shift posed a danger to residents' health and violated the Charter of Rights. Last year a National Steering Committee on Resident Duty Hours said the status quo was unacceptable and that shifts of 24 hours or longer without sleep should be avoided. It urged all provinces and health care institutions to develop comprehensive strategies to minimize fatigue and fatigue-related risks during residency.

Dr. Najma Ahmad, a trauma surgeon at St. Michael's Hospital who was a member of the national group, published a paper today in the Annals of Surgery that found the too-restricted hours may work for some residents, but not for surgical residents.

"A one-size fits all approach to resident duty hours may not be appropriate for all specialties," said Dr. Ahmed, noting that the American College of Surgeons Division of education has stated that mastery in surgery requires "extensive and immersive experiences."

She said the emphasis should be on reducing the amount of non-educational work residents do and to find ways to manage fatigue such as making sure they get enough uninterrupted sleep. Dr. Ahmed, who is also director of the University of Toronto's General Surgery Program, conducted a meta-analysis of 135 articles on the impact of resident duty hours on clinical and educational outcomes in surgery.

"In surgery, recent changes in hours for residents are not consistently associated with improved resident well-being and may have negative impacts on patient outcomes and performance on certification exams," she said.

Dr. Ahmed said that shorter hours for residents means more shift handovers, which means less continuity of care and more opportunities for information to get lost or not passed along. Shorter shifts may also reduce residents' ability to observe the natural course of a patient's recovery and recognize when a patient starts to experience complications.

"We must remember that the objective of residencies is to train expert clinicians. In the case of surgery, this requires a lot of time in the operating room, under the mentorship of an expert surgeon. Coaching in the operating room specifically requires that mentors observe progress, provide feedback and then look for progress at the next opportunity."