A laboratory comparison of clockwise and counter-clockwise rapidly rotating shift schedules, part I, sleep.

Civil Aerospace Medical Institute2002PDFTech ReportCruz, Crystal E.Detwiler, C.Nesthus, Thomas E.Boquet, A.Civil Aerospace Medical InstituteUnited States. Office of Aerospace MedicineCivil Aerospace Medical InstituteUnited StatesShiftsAir traffic controlAlternatives analysisHuman factorsLaboratory testsSleepCircadian rhythmsData analysisShiftworksleepcircadian rhythmsDOT/FAA/AM-02/8INTRODUCTION. 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. METHODS. 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. RESULTS. Both groups reported less sleep before the early morning shifts (MClockwise=5.1h; Mcounter-clockwise=5.5h) than before the afternoon shifts (MClockwise=7.5h; Mcounter-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. DISCUSSION. 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.119