Comparison of a Circadian-based and a Forward Rotating Watch Schedules on Sleep,Mood,and Psychomotor Vigilance Performance

Abstract

In the military, any degradation in performance may have serious implications, potentially resulting in loss of life or affecting mission accomplishment. The maritime environment imposes the additional unique challenges of waterborne motion on the shipboard crew. Additionally, the U.S. Navy’s 24/7 operational requirements mandate rigorous equipment monitoring and shiftwork. This study assesses how crewmember sleep hygiene and psychomotor vigilance performance is affected by a shift from traditional work schedules to an alternative circadian-based schedule. Twenty-eight sailors were assessed while working two watch schedules, a conventional 5-hours on/10-hours off (5/10) rapidly rotating schedule, and an alternative 3-hours on/9-hours off (3/9) fixed schedule. Average daily sleep duration was the same for both watch schedules. However, compared to their scores on the 5/10, sailors on the 3/9 had significantly less daytime sleepiness, improved mood, 30% faster reaction times, and had 40% to 50% fewer errors (i.e., lapses combined with false starts). The significant improvements in performance, mood, and sleep hygiene observed in this within-subjects study suggest that circadian watch schedules should be chosen rather than non-circadian aligned schedules.