Effect of a Protected Sleep Period on Hours Slept During Extended Overnight In-Hospital Duty Hours Among Medical Interns: A Randomized Trial

Study Questions:

What are the feasibility and consequences of protected sleep periods during extended duty?


A randomized, controlled trial was conducted at the VA Medical Center medical service and oncology unit of the Hospital of the University of Pennsylvania (2009-2010). Of the 103 participating interns and senior medical students, 44 worked at the VA center, 16 at the university hospital, and 43 at both. Twelve 4-week blocks were randomly assigned to either a standard intern schedule (extended duty overnight shifts of up to 30 hours; equivalent to 1,200 overnight intern shifts at each site), or a protected sleep period (protected time from 12:30 a.m. to 5:30 a.m. with handover of work cell phone, equivalent to 1,200 overnight intern shifts at each site). Participants wore wrist actigraphs and complete sleep diaries. Primary outcome was hours slept during the protected period on extended duty overnight shifts. Secondary outcome measures included hours slept during a 24-hour period (noon to noon) by day of call cycle and Karolinska sleepiness scale.


For 98.3% of on-call nights, cell phones were signed out as designed. At the VA center, participants with protected sleep had a mean 2.86 hours (95% confidence interval [CI], 2.57-3.10 hours) of sleep versus 1.98 hours (95% CI, 1.68-2.28 hours) among those who did not have protected hours of sleep (p < 0.001). At the university hospital, participants with protected sleep had a mean 3.04 hours (95% CI, 2.77-3.45 hours) of sleep versus 2.04 hours (95% CI, 1.79-2.24) among those who did not have protected sleep (p < 0.001). Participants with protected sleep were significantly less likely to have call nights with no sleep: 5.8% (95% CI, 3.0%-8.5%) versus 18.6% (95% CI, 13.9%-23.2%) at the VA center (p < 0.001) and 5.9% (95% CI, 3.1%-8.7%) versus 14.2% (95% CI, 9.9%-18.4%) at the university hospital (p = 0.001). Participants felt less sleepy after on-call nights in the intervention group, with Karolinska sleepiness scale scores of 6.65 (95% CI, 6.35-6.97) versus 7.10 (95% CI, 6.85-7.33; p = 0.01) at the VA center and 5.91 (95% CI, 5.64-6.16) versus 6.79 (95% CI, 6.57-7.04; p < 0.001) at the university hospital.


For internal medicine services at two hospitals, implementation of a protected sleep period while on call resulted in an increase in overnight sleep duration and improved alertness the next morning.


This is a very interesting and important study supporting a protected sleep period for students and junior house staff. I am surprised that during the protected sleep time, the participants averaged only 3 hours of sleep. The authors speculated that sleep periods many have been influenced by stress and physical discomfort because the rate of sleep disturbance from cell phone, pagers, and nurses was only about 5%, compared to about 70% in the controls. Similar studies are needed for surgery and obstetrics-gynecology.

Clinical Topics: Anticoagulation Management, Sleep Apnea

Keywords: Students, Outcome Assessment (Health Care), Natriuretic Peptides, Life Style, Cellular Phone, Sleep Stages, Cardiology, Sleep Deprivation, Sleep Disorders, Peptide Fragments, Internal Medicine, Hospital Communication Systems

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