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Giving residents less time on duty and more time to sleep was supposed to lead to fewer medical errors. But the latest research shows that’s not the case. What’s going on?

Since 2011, new regulations restricting the number of continuous hours first-year residents spend on call cut the time that trainees spend at the hospital during a typical duty session from 24 hours to 16 hours. Excessively long shifts, studies showed, were leading to fatigue and stress that hampered not just the learning process, but the care these doctors provided to patients.

And there were tragic examples of the high cost of this exhausting schedule. In 1984, 18-year-old Libby Zion, who was admitted to a New York City hospital with a fever and convulsions, was treated by residents who ordered opiates and restraints when she became agitated and uncooperative. Busy overseeing other patients, the residents didn’t evaluate Zion again until hours later, by which time her fever has soared to 107ºF (41.7ºC) and she went into cardiac arrest and died. The case highlighted the enormous pressures on doctors in training and the need for reform in the way residents were taught. In 1987, a New York State commission limited the number of hours that doctors could train in the hospital to 80 each week, which was less than the 100-hour-a-week shifts with 36-hour call times that were the norm at the time. In 2003, the Accreditation Council for Graduate Medical Education followed suit with rules for all programs that mandated that trainees could work no more than 24 consecutive hours.

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In 2011, those hours were cut even further, but the latest data, published online in JAMA Internal Medicine, found that interns working under the new rules are reporting more mistakes, not enough sleep and symptoms of depression. In the study that involved 2,300 doctors from more than a dozen national hospitals, the researchers compared a population of interns serving before the 2011 work-hour limit was implemented, with interns working after the new rule, during a three-month period. Those in the former group were on call every fourth night, for a maximum of 30 hours, while the latter group worked no more than 16 hours during any one shift. They gathered self-reported data from on their duty hours, sleep hours, symptoms of depression, well-being and medical errors at three, six, nine and 12 months into their first year of residency.

Although the trainees working under the current work rules spent fewer hours at the hospital, they were not sleeping more on average than residents did prior to the rule change, and their risk of depression remained the same, at 20%, as it was among the doctors working prior to 2011. And the number of medical errors the post-2011 doctors reported was higher than that documented among previous trainees. “In the year before the new duty-hour rules took effect, 19.9% of the interns reported committing an error that harmed a patient, but this percentage went up to 23.3% after the new rules went into effect,” said study author Dr. Srijan Sen, a University of Michigan psychiatrist in a statement. “That’s a 15% to 20% increase in errors — a pretty dramatic uptick, especially when you consider that part of the reason these work-hour rules were put into place was to reduce errors.”

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How could fewer hours lead to more errors? For one, interns reported that while they weren’t working as many hours, they were still expected to accomplish the same amount that previous classes had, so they had less time to complete their duties. According to the study authors, this may be leading to work compression, and that can increase the risk of errors or mistakes if residents don’t have as much time to make and recheck patient-care decisions. In addition, the pressure may be even greater for residents in many hospitals where the new restrictions on hours were not accompanied by funding to hire new staff to balance the workload.

“For most programs the significant reduction in work hours has not been accompanied by any increase in funding to off-load the work. As a result, though many programs have made some attempts to account for this lost work in other ways, the end result is that current interns have about 20 less hours each week to complete the same or only slightly less work. If we know that timed tests result in more errors than untimed ones, we should not be surprised that giving interns less time to complete the same amount of work would increase their errors as well,” said study author Dr. Breck Nichols, the program director of the combined internal-medicine and pediatrics residency program at the University of Southern California, in a statement.

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Another source of errors came as one intern going off duty handed his cases to another. With fewer work hours, the researchers say the number of handoffs has increased, from an average of three during a single shift to as many as nine. Anytime a doctor passes on care of a patient to another physician, there is a chance for error in communicating potential complications, allergies, or other aspects of the patient’s health; that risk is boosted when the transition occurs several times over.

In 2011, Dr. Zachary F. Meisel, a practicing emergency physician and an assistant professor of emergency medicine at the Perelman School of Medicine at the University of Pennsylvania, and Dr. Jesse M. Pines, the director of the Center for Health Care Quality and an associate professor of emergency medicine at George Washington University, wrote in TIME about how dicey more handoffs could be:

Shorter shifts mean more potentially dangerous handoffs, wherein doctors and nurses transfer the care of their patients to a new shift worker who is not as familiar with the patients’ histories and may be less emotionally invested in their care. Handoffs are notoriously fraught with miscommunication and are known to create opportunity for mistakes.

Their suggestion at the time was to encourage napping on the job to improve current problems in sleepy doctors, citing studies showing sleep improving performance and that instituting naps actually did result in more rest among medical residents. They write:

For those of us who trained under the old never-sleep, always-take-care-of-your-own-patients-at-all-costs, tough-it-out system, restrictions on work hours seem soft. Napping in the middle of a shift? That’s a sign of downright weakness. But this persistent macho attitude is part of the problem. Sleep science and studies of shift workers in nonmedical disciplines have repeatedly shown that tired workers not only make more mistakes, but also often fail to identify their own fatigue. Letting tired doctors and nurses take naps, or even forcing them to, may be a workable solution.

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The authors of the current study acknowledge that their findings are preliminary and based on reports of depressive symptoms, sleep and medical errors that were reported by the residents themselves. They acknowledge that it may simply take time for the health care system to adjust to the new rules, since long hours have been so ingrained in medical training. But the results hint at some potential unintended consequences of the more restrictive hours that may need adjusting in the coming years. Fewer hours at the hospital means less time for residents to train and learn the skills they need to care for patients; even the staple of resident training, the daily rounds, in which experienced physicians and residents visit each patient admitted to the hospital under their care to review, have been cut short because of the limited hours that residents have on duty.

Figuring out the right balance between humane work conditions that promote the best learning environment for residents and the highest quality of care for patients may still be a work in progress. More research is needed to pinpoint what’s driving the uptick in medical errors and determining the best strategies for improving resident training to bring these rates down.