Clockwise and counterclockwise rotating shifts: effects on sleep duration, timing, and quality.
BACKGROUND
Many air traffic control specialists (ATCS) work relatively unique counterclockwise, rapidly rotating shift schedules. Researchers recommend, however, that if rotating schedules are to be used, they should rotate in a clockwise (CW), rather than a counterclockwise (CCW) direction. Unfortunately, few studies have examined CW and CCW rapidly rotating shifts. This study was designed to partially remedy this lack by examining the effects of both types of schedules on sleep duration, timing, and quality.


METHODS
Participants (n = 28) worked a week of day shifts (0800-1600 h) followed by two weeks of either a CW (n = 14) or CCW (n = 14) shiftwork schedule, including early morning (0600-1400 h), afternoon (1400-2200 h), and midnight shifts (2200-0600 h). Participants recorded sleep data and subjective ratings of sleep quality, sleepiness, and mood in daily logbooks and wore wrist activity sensors to provide an objective source of sleep/wake data.


RESULTS
There was no effect of rotation condition for any of the sleep measures. A main effect for Sleep Period (F (5,16) = 40.9, p < 0.05) indicated that both groups received less sleep prior to the early morning shifts than before the afternoon and midnight shifts. Sleepiness ratings were highest at the end of the midnight shift.


CONCLUSIONS
Rotation condition did not play a significant role in the results of any of the sleep or subjective measures. The results of this study indicate that two problem areas in both CW and CCW rapidly rotating shift schedules are early morning and midnight shifts.
Cruz
Crystal
C
Federal Aviation Administration, Civil Aerospace Medical Institute, Oklahoma City, OK 73125, USA. crystal.cruz@faa.gov
Detwiler
Cristy
C
Nesthus
Thomas
T
Boquet
Albert
A
D001359:Aviation; D006801:Humans; D012890:Sleep; D014940:Work Schedule Tolerance