The Accreditation Council for Graduate Medical Education (ACGME) sets rules for most graduate-level training programs for doctors in the United States.

In 2003, the group shortened working hours for U.S. doctors-in-training, known as residents. It limited their work duties to 80 hours a week.

The move caused some members of the medical community to raise questions: Did the reduced hours give residents enough time to learn the art of medicine? And, would future patients suffer?

Now, a study has answers. It found no difference in hospital deaths, hospital readmissions or costs when comparing results from doctors trained before and after the hour limits. The findings appeared in the medical publication BMJ.

FILE - In this Wednesday, Sept. 23, 2015 photo, Dr. Rick Sacra reviews patient cases with Dr. Anna Chon at the Family Health Center in Worcester, Mass., where he advises doctors in training.

The debate about how much time hospital residents should work has a long history. The ACGME notes that as early as the 1970s, studies found that residents were more likely to make mistakes when they failed to get enough sleep.

In 1984, college freshman Libby Zion died a short time after being admitted to an emergency room at a New York hospital. A grand jury investigation found that the long work hours required of residents were partly to blame for her death. In some cases, residents worked as many as 36 hours straight.

"Some (people) still long for the old days of 100-hour work weeks, but most of the world has moved on and realized there are better ways to train residents," noted Karl Bilimoria. He is a doctor with the Northwestern University Feinberg School of Medicine. He was not involved in the study.

Bilimoria added that training could become more effective by reducing paperwork and attendance at academic conferences. He also likes the idea of adding more nurse practitioners to the medical workforce.

Earlier studies suggested the 2003 reforms did not harm residents' patients. The new study is the first to find similar results for doctors once they work in the real world, notes Doctor Mitesh Patel of the University of Pennsylvania. He was not involved with the study.

Isaiah Cochran worked 75 hours a week, including some 16-hour shifts, at Dayton Children's Hospital in Ohio during his last year of medical school.

"It's doable. It's not insane," said Cochran, who serves as president of the American Medical Student Association. His group supports keeping the 80-hour limit and other measures aimed at making sure residents get enough rest.

For the study, researchers looked at records from more than 400,000 hospitalizations of U.S. patients. Each of the patients was covered under Medicare, the national health insurance program.

Using billing information, the researchers identified a doctor who dealt with each patient the most. Then they compared cases from two six-year time periods: before and after 2006. That is the year when the first new doctors who were fully affected by the reforms finished their residencies.

The researchers found no difference in patient deaths, hospital readmissions or costs.

Patients depend on teams of health care workers, not just one doctor, and that may explain why doctor training time seemed to have no effect on care.

Teamwork and technology have changed hospital care so much that the effect of any one doctor is not great, said Anupam Jena of Harvard Medical School. Doctor Jena was the lead author of the published report on the study.

And more change is expected with artificial intelligence. With computers taking a larger role in diagnosis and treatment, Jena said, "it should be an open question whether 80 hours a week is the right number" for training. Maybe it could be less.

The results apply to doctors specializing in internal medicine, not surgeons. More research is needed on whether surgeons are getting enough experience during training, Jena said.

And I'm John Russell.

Carla K. Johnson reported on this story for the Associated Press. John Russell adapted her story for Learning English. George Grow was the editor.

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