A laboratory comparison of clockwise and counter-clockwise rapidly rotating shift schedules: Part I. Sleep.

Abstract

Abstract : Many air traffic control specialists work relatively unique counter-clockwise, rapidly rotating shift schedules. Researchers recommend, however, that if rotating schedules are to be used, they should rotate in a clockwise, rather than a counterclockwise direction. Unfortunately, few studies have examined clockwise and counter-clockwise, 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. Participants (n = 28) worked a week of day shifts (0800-1600), followed by two weeks of either a Clockwise (n = 14) or Counter-Clockwise (n = 14) shiftwork schedule, including early morning (0600-1400), afternoon (1400-2200), and midnight shifts (2200-0600). Participants recorded sleep data in daily logbooks and wore wrist activity sensors to provide an objective source of sleep/wake data. Both groups reported less sleep before the early morning shifts (M(sub Clockwise) = 5.1h; M(sub counter-clockwise) = 5.5h) than before the afternoon shifts (M(sub Clockwise) = 7.5h; M(sub counter-Clockwise) = 7.9h). The Clockwise group reported an average of 7.2h of sleep during the night before the midnight shifts and a nap during the day of 0.9h. In addition to a nighttime sleep of 6.0h, the Counter-Clockwise group also took a nap before the midnight shifts of 2.2h. Objective sleep data and subjective sleep quality ratings are also reported. While these data indicate that a longer concentrated sleep period is obtained prior to the midnight shift on the Clockwise rotation schedule, they do not fully support the hypothesis that a clockwise rotation will result in less sleep disruption.