On Saturday, 30,000 first-year medical residents begin work and new rules taking effect that same day could add eight or more hours to their shifts.
Doctors fresh out of medical school will be able toinstead of the previous limit of 16 hours, raising concerns about patient safety.
But many are actually welcoming the longer days, reports CBS News medical contributor Dr. Tara Narula.
The issue has been under the microscope for three decades. It's a balancing act to determine the ideal working hours for both medical care and on-the-job training.
Melissa Garuthara's day starts at 5 a.m., when she reports for rounds at Long Island Jewish Medical Center.
During her first year as a doctor, she was required to clock out after 16 hours, even when she wanted to stay longer.
"I don't want to say, 'Oh, you know, I'm leaving for the day but the night intern is going to come and check on you.' I want to be the one doing that," Garuthara said.
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Shorter shifts mean more frequent handoffs, bringing more opportunity for and interruptions to doctor training.
"Medical emergencies don't all occur between 8 and 4," said Dr. Rowen Zetterman, who helped helped update the rules to bring training in line with the realities of hospital care.
"When you had one resident who was only there 16 hours, and another one that was there 24, it interfered with the team-based care that occurred," Zetterman said.
Another key goal of the new rules is to help doctors become more invested in their patients by avoiding a shift-work mentality.
Under the new rules, first-year residents can choose to stay even longer than 24 hours, to an average maximum of 80 hours per week.
But Dr. Sammy Almashat, who tracks doctor training for Public Citizen, believes the change has a serious downside.
"Keep in mind interns have just graduated medical school. They are the least experienced, the least knowledgeable members of the medical team caring for patients," Almashat said.
Asked whether the longer hours can be detrimental to patients and residents, Almashat said, "Yes, that's what the evidence shows, unequivocally."
A Harvard study found that residents made almost 36 percent more serious medical errors when working 24 hours or longer.
"They're coming up against their limits of their capacity to function and all they can think about is sleep," according to Almashat.
Now starting year two, Garuthara says extended hours might have enhanced her first-year training.
"I can read about it, I can watch YouTube, I can do anything on it from home but it's not going to be the same as, you know, being bedside with a patient," Garuthara said.
Asked whether she often hears residents commiserate about long hours and fatigue, Garuthara said, "Obviously, some people. We can get tired. But I think that the idea of the intern as a creature that lives in the hospital and comes out after 30 hours in like a dark closet, I think that's kind of archaic now," she said.