The first study to assess the benefits of naps for medical residents during extended shifts found that creating protected times when interns could sleep during a night on-call significantly reduced fatigue.
In the June 6, 2006, issue of the Annals of Internal Medicine, researchers from the University of Chicago report that although average sleep time for interns in the study increased only modestly -- by about one hour -- the interns felt that even small gains in sleep led to substantial improvements in fatigue, sleep quality and ability to care for their patients.
"This is a proven method of alleviating fatigue in industries that combine high intensity with long shifts," said study director Vineet Arora, M.D., instructor of medicine at the University of Chicago, "yet is has been neglected by the one industry that studies sleep. Our results show that a well timed nap can provide a significant boost in physician concentration and take away some of the burden of chronic sleep deprivation."
The researchers studied 38 first-year medical residents (also known as interns) on the general medicine service at the University of Chicago Hospital from July 2003 to June 2004. For several month-long periods during that year, the interns were on-call every fourth night. Interns on-call often work a 30-hour shift, consisting of a full day, then a night on-call, followed by a shorter day. Each intern wore an "Actiwatch" for the entire month, which recorded his or her movements around the hospital, time in bed and time asleep.
For two weeks out of each month on-call, interns followed the standard schedule, grabbing a little sleep whenever they could during the night shift. For the other two weeks they had access to protected time, allowing them to nap. Those on the nap schedule were "strongly encouraged" to forward the care of their patients to a designated "night-float" resident who would cover for them between midnight and 7 a.m.
During 119 total months on service, the 38 interns were randomly prompted during on-call and post-call days (but not between midnight and 7 a.m.) to report their fatigue at that moment, using the seven-point Stanford Sleepiness Scale. One point indicates "feeling active and vital, alert, wide awake," and seven points indicates "almost in reverie, sleep onset soon, losing struggle to remain awake."
Interns on the nap schedule increased their average sleep time by 41 minutes, from 144 minutes a night up to 185 minutes. Interns on the nap schedule who forwarded their pagers to the "night-float" resident increased their sleep times even more, from 142 up to 210 minutes. Sleep efficiency – the ration between time in bed and time asleep – also improved for those on the nap schedule, from 73 percent, considered abnormal, up to 80 percent.
When prompted, interns on the nap schedule reported far less fatigue. They logged an overall sleepiness rating of 1.74 compared to 2.26 for those on the standard schedule. (Lower is better.) They had lower scores while on call, 1.59 versus 2.06, and much lower scores the day after being on call, 2.23 versus 3.16.
"A rating of one or even two is consistent with peak performance," said Arora, but people may start to get "sluggish," she said, at three. Anything above three is "clinically relevant."
The researchers found, however, that despite mounting fatigue and the allure of protected sleep time, interns were reluctant to rely on the night-float residents, forwarding their pagers only 22 percent of available opportunities. When interviewed, interns emphasized the importance of caring for their own patients and concerns about losing important information whenever responsibility is transferred back and forth with another physician.
"Our study," the authors wrote, "suggests that these young physicians are choosing to care for their patients over their own immediate welfare."
Although interns did not mind sacrificing sleep for their own patients, they did not feel the same allegiance when they had to "cross-cover" patients whom they did not know to help other physicians. Many found ways to retain the pages for their own patients but were happy to transfer others to the night-float resident.
At a time, the authors note, when newly imposed restrictions on resident hours result in more frequent cross-coverage, "this finding is concerning."
As hospitals nationwide search for ways to reduce resident sleep deprivation, many have considered shorter shifts. This study suggests that an extended long shift, punctuated by a substantial nap, may be more effective, reducing levels of resident fatigue but also limiting the amount of time that patients would be cared for by covering physicians, "a known risk factor for preventable adverse effects."
In response to this study, all interns on the general medicine service at the University of Chicago Hospitals now have access to night-float coverage and are encouraged to take advantage of the opportunity to sleep.
The study was funded by the department of medicine and the Pritzker School of Medicine at the University of Chicago. Additional authors include Carrie Dunphy, Vivian Chang, Fawaz Ahmad, Holly Humphrey and David Meltzer, all from the University of Chicago.
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