Do split sleep and wake times increase or reduce sleepiness during nonstop work?

On average, subjective sleepiness was significantly higher during wake periods in the split sleep/wake schedule than during the first half of wake periods in the consolidated schedule.

• The study involved 29 healthy adult males, with 13 in the consolidated sleep/wake group and 16 in the split sleep/wake group.
• Both sleep/wake schedules included 7×28-h days with 9.33 hours of sleep and 18.67 hours of wake each day.
• The split sleep/wake protocol consisted of 2×4.67-hour sleep opportunities and 2×9.33-hour wake periods each day.
• Subjective sleepiness was measured using the Karolinska Sleepiness Scale every 2.5 hours during waking hours.
• Feelings of sleepiness for split schedules were greater than for consolidated schedules during at least half of the awake time.

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