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Sleep. 2017 Apr 1;40(4). doi: 10.1093/sleep/zsx027.

Sleep and Alertness in Medical Interns and Residents: An Observational Study on the Role of Extended Shifts.

Author information

Unit for Experimental Psychiatry, Division of Sleep and Chronobiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA.
Center for Health Equity Research and Promotion, Philadelphia Corporal Michael J. Cresencz Veterans Affairs Medical Center, Philadelphia, PA.
Department of Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA.
Leonard Davis Institute Center for Health Incentives and Behavioral Economics, University of Pennsylvania, Philadelphia, PA.
Department of Statistics, The Wharton School, University of Pennsylvania, Philadelphia, PA.
Department of Health Care Management, The Wharton School, University of Pennsylvania, Philadelphia, PA.
Department of Medical Ethics and Health Policy, University of Pennsylvania, Philadelphia PA.


Study Objectives:

Fatigue from sleep loss is a risk to physician and patient safety, but objective data on physician sleep and alertness on different duty hour schedules is scarce. This study objectively quantified differences in sleep duration and alertness between medical interns working extended overnight shifts and residents not or rarely working extended overnight shifts.


Sleep-wake activity of 137 interns and 87 PGY-2/3 residents on 2-week Internal Medicine and Oncology rotations was assessed with wrist-actigraphy. Alertness was assessed daily with a brief Psychomotor Vigilance Test (PVT) and the Karolinska Sleepiness Scale.


Interns averaged 6.93 hours (95% confidence interval [CI] 6.84-7.03 hours) sleep per 24 hours across shifts, significantly less than residents not working overnight shifts (7.18 hours, 95% CI 7.06-7.30 hours, p = .007). Interns obtained on average 2.19 hours (95% CI 2.02-2.36 hours) sleep during on-call nights (17.5% obtained no sleep). Alertness was significantly lower on mornings after on-call nights compared to regular shifts (p < .001). Naps between 9 am and 6 pm on the first day post-call were frequent (90.8%) and averaged 2.84 hours (95% CI 2.69-3.00 hours), but interns still slept 1.66 hours less per 24 hours (95% CI 1.56-1.76 hours) compared to regular shift days (p < .001). Sleep inertia significantly affected alertness in the 60 minutes after waking on-call.


Extended overnight shifts increase the likelihood of chronic sleep restriction in interns. Reduced levels of alertness after on-call nights need to be mitigated. A systematic comparison of sleep, alertness, and safety outcomes under current and past duty hour rules is encouraged.



actigraphy; alertness; effects of sleep restriction on cognition and affect.; fatigue; medical education; medical interns; psychomotor vigilance performance; shiftwork; sleep deprivation

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