Systematic review: association of shift length, protected sleep time, and night float with patient care, residents' health, and education

Ann Intern Med. 2010 Dec 21;153(12):829-42. doi: 10.7326/0003-4819-153-12-201012210-00010.


Background: The Accreditation Council for Graduate Medical Education's new duty-hour standards limit interns' shifts to 16 hours and night float to 6 consecutive nights. Protected sleep time (that is, "nap") is strongly encouraged. As duty-hour reforms are implemented, examination of the quality and outcomes of the relevant literature is important.

Purpose: To systematically review the literature examining shift length, protected sleep time, and night float.

Data sources: MEDLINE, PREMEDLINE, and EMBASE from January 1989 through May 2010.

Study selection: Studies examined the associations of shift length, protected sleep time, or night float with patient care, resident health, and education outcomes among residents in practice settings.

Data extraction: Study quality was measured by using the validated Medical Education Research Study Quality Instrument and the U.S. Preventive Services Task Force criteria. Two investigators independently rated study quality, and interrater agreement was calculated.

Data synthesis: Sixty-four studies met inclusion criteria. Most studies used single-group cross-sectional (19 studies [29.7%]) or pre-post (41 studies [64.1%]) designs, and 4 (6.3%) were randomized, controlled trials. Five studies (7.8%) were multi-institutional. Twenty-four of 33 (72.7%) studies examining shift length reported that shorter shifts were associated with decreased medical errors, motor vehicle crashes, and percutaneous injuries. Only 2 studies assessed protected sleep time and reported that residents' adherence to naps was poor. Night floats described in 33 studies involved 5 to 7 consecutive nights.

Limitations: Most studies used single-institution, observational designs. Publication bias is likely but difficult to assess in this methodologically weak and heterogeneous body of evidence.

Conclusion: For the limited outcomes measured, most studies supported reducing shift length but did not adequately address the optimal shift duration. Studies had numerous methodological limitations and unclear generalizability for most outcomes. Specific recommendations about shift length, protected sleep time, and night float should acknowledge the limitations of this evidence.

Primary funding source: Accreditation Council for Graduate Medical Education.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review
  • Systematic Review

MeSH terms

  • Educational Measurement
  • Health Status
  • Humans
  • Internship and Residency / standards*
  • Patient Care / standards*
  • Personnel Staffing and Scheduling / standards*
  • Sleep*
  • Time Factors
  • Work Schedule Tolerance*