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Randomized Controlled Trial
. 2019 Mar 7;380(10):915-923.
doi: 10.1056/NEJMoa1810641.

Sleep and Alertness in a Duty-Hour Flexibility Trial in Internal Medicine

Mathias Basner  1 , David A Asch  1 , Judy A Shea  1 , Lisa M Bellini  1 , Michele Carlin  1 , Adrian J Ecker  1 , Susan K Malone  1 , Sanjay V Desai  1 , Alice L Sternberg  1 , James Tonascia  1 , David M Shade  1 , Joel T Katz  1 , David W Bates  1 , Orit Even-Shoshan  1 , Jeffrey H Silber  1 , Dylan S Small  1 , Kevin G Volpp  1 , Christopher G Mott  1 , Sara Coats  1 , Daniel J Mollicone  1 , David F Dinges  1 ; iCOMPARE Research Group
Collaborators, Affiliations
Randomized Controlled Trial

Sleep and Alertness in a Duty-Hour Flexibility Trial in Internal Medicine

Mathias Basner et al. N Engl J Med. .

Abstract

Background: A purpose of duty-hour regulations is to reduce sleep deprivation in medical trainees, but their effects on sleep, sleepiness, and alertness are largely unknown.

Methods: We randomly assigned 63 internal-medicine residency programs in the United States to follow either standard 2011 duty-hour policies or flexible policies that maintained an 80-hour workweek without limits on shift length or mandatory time off between shifts. Sleep duration and morning sleepiness and alertness were compared between the two groups by means of a noninferiority design, with outcome measures including sleep duration measured with actigraphy, the Karolinska Sleepiness Scale (with scores ranging from 1 [extremely alert] to 9 [extremely sleepy, fighting sleep]), and a brief computerized Psychomotor Vigilance Test (PVT-B), with long response times (lapses) indicating reduced alertness.

Results: Data were obtained over a period of 14 days for 205 interns at six flexible programs and 193 interns at six standard programs. The average sleep time per 24 hours was 6.85 hours (95% confidence interval [CI], 6.61 to 7.10) among those in flexible programs and 7.03 hours (95% CI, 6.78 to 7.27) among those in standard programs. Sleep duration in flexible programs was noninferior to that in standard programs (between-group difference, -0.17 hours per 24 hours; one-sided lower limit of the 95% confidence interval, -0.45 hours; noninferiority margin, -0.5 hours; P = 0.02 for noninferiority), as was the score on the Karolinska Sleepiness Scale (between-group difference, 0.12 points; one-sided upper limit of the 95% confidence interval, 0.31 points; noninferiority margin, 1 point; P<0.001). Noninferiority was not established for alertness according to the PVT-B (between-group difference, -0.3 lapses; one-sided upper limit of the 95% confidence interval, 1.6 lapses; noninferiority margin, 1 lapse; P = 0.10).

Conclusions: This noninferiority trial showed no more chronic sleep loss or sleepiness across trial days among interns in flexible programs than among those in standard programs. Noninferiority of the flexible group for alertness was not established. (Funded by the National Heart, Lung, and Blood Institute and American Council for Graduate Medical Education; ClinicalTrials.gov number, NCT02274818.).

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Figures

Figure 1.
Figure 1.. Noninferiority Analyses for Sleep Duration, Sleepiness, and Alertness.
Shown are unadjusted 95% confidence intervals for the difference between interns in flexible programs and those in standard programs, with respect to average sleep duration per 24 hours (Panel A), average score on the Karolinska Sleepiness Scale (Panel B), and average number of performance lapses on the brief Psychomotor Vigilance Test (PVT-B) (Panel C). Scores on the Karolinska Sleepiness scale range from 1 (extremely alert) to 9 (extremely sleepy, fighting sleep); performance lapses on the PVT-B were defined as reaction times of more than 355 msec, with a higher number of lapses indicating lower levels of alertness. Noninferiority tests were one-sided, with noninferiority margins of −0.5 hour, 1 point on the Karolinska Sleepiness Scale, and 1 additional lapse on the PVT-B, respectively. Analyses indicate that the sleep duration per 24 hours and subjective ratings of sleepiness in flexible programs were noninferior to those in standard programs, whereas noninferiority was not established for objectively assessed alertness according to the PVT-B. Sleep duration and the score on the Karolinska Sleepiness Scale in flexible programs remained noninferior to those in standard programs at an alpha level of 0.05 after Benjamini–Hochberg adjustments for multiple testing (three comparisons). The 95% confidence intervals in the figure have not been adjusted for multiple comparisons, and inferences drawn from these intervals may not be reproducible.
Figure 2.
Figure 2.. Different Shift Types in Standard and Flexible Programs.
Gray bars depict typical work periods for the different shift types in standard and flexible programs. Interns were instructed to take the survey and PVT-B between 6 a.m. and 9 a.m. every day. An extended overnight shift in flexible programs spanned across 2 days. The work period started in the morning of day 1 and concluded at approximately noon on day 2. In this shift, the survey and PVT-B were administered once at the beginning of the shift on day 1 and a second time 24 hours later close to the end of the shift on day 2. The actual placement and duration of shifts in standard and flexible programs may have differed for individual programs.
Figure 3.
Figure 3.. Percent of Interns Sleeping According to Time of Day.
The sleep duration of interns in flexible programs was more than 2 hours shorter on the second day of the extended overnight shift than that during the regular night shifts of interns in standard programs (Panel A). Interns in flexible programs slept longer before extended overnight shifts (Panel B), before day shifts (Panel C), and before days off (Panel D) than interns in standard programs.
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