O067 Comparison of Sleep Quantity and Quality during Watchkeeping Schedules

Watchkeeping schedules expose workers to sleep and wake opportunities which are not at biologically ideal times, thus impacting sleep quantity and quality. This study investigated the impact of different watchkeeping schedules on sleep. N=29 healthy participants (16F; aged 18-34y) took part in a 10-day laboratory study. Participants were allocated to one of four schedules; 8h-on/8h-off/4h-on/4h-off (day-sleep 09:30-16:00; n=8; Condition A), 6h-on/6h-off (day-sleep 08:30h-12:30, nap 21:30-00:00; n=7; Condition B), and 4h-on/4h-on-call/4h-off/4h-on/8h-off (evening-sleep 18:00-00:30; n=7; Condition C; or night-sleep 01:30h-08:00; n=7; Condition D). Participants had 8h time in bed (TIB) for sleep at baseline and recovery. Every 24h during the schedule, participants received a 6.5h TIB. Sleep was measured using standard polysomnography and scored by a trained sleep technician. Linear mixed models found that Condition D (night sleep) had significantly longer total sleep time (TST) than Condition B (p=.003; split sleep). Participants obtained significantly less TST on Day 2 compared to remaining experimental days (Day 3 to Day 8; p<.05). Sleep onset latency was longer on Day 8, than Days 2 and 3 (p<.01). Time spent in REM sleep was shorter on Days 2 and 3 than any other days (p<.05). There were no differences in sleep stages between conditions, except for TST. The split sleep in Condition B resulted in less sleep. Shorter TST at the beginning of the study may indicate the adjustment period of the new sleep/wake schedule. These results reveal that there are implications for sleep when sleep periods are reduced during watchkeeping.