Sleep and performance in simulated Navy watch schedules

Area of Science:

• Maritime operations
• Sleep science
• Human performance

Background:

• Continuous 24/7 Navy ship operations necessitate watchstanding schedules.
• Common schedules include 5/15 (5h on, 15h off) and 3/9 (3h on, 9h off) systems.
• These schedules impact sleep timing and duration, potentially affecting crew well-being and performance.

Purpose of the Study:

• To compare the effects of simulated 5/15 and 3/9 Navy watch schedules on sleep duration, psychomotor vigilance, and subjective sleepiness.
• To assess the impact of cumulative sleep loss and fatigue in these operational contexts.

Main Methods:

• Fifteen healthy male subjects participated in a 6-day laboratory study.
• Sleep opportunities were restricted to an average of 6.5 hours daily.
• Sleep duration, psychomotor vigilance, and sleepiness were measured using actigraphy and performance tests.

Main Results:

• Average sleep duration was 5.6 hours per day, with no significant difference between the 5/15 and 3/9 schedules.
• Sleep duration was not significantly affected by split sleep opportunities.
• Psychomotor vigilance declined over the study days, showing greater variability in the 5/15 schedule compared to the 3/9 schedule.

Conclusions:

• Both 5/15 and 3/9 Navy watch schedules are associated with cumulative sleep loss and fatigue.
• The fixed watch periods of the 3/9 schedule appear to support more consistent performance than the backward-rotating 5/15 schedule.
• Optimizing Navy operations may require longer and more consistent daily sleep opportunities than currently implemented.