O034 Rockabye sailor: investigating the impact of simulated motion on sleep and cognitive performance

BACKGROUND: Many naval vessels are designed with sleeping berths orientated in a fore/aft direction. Reorientating the berths changes the rocking from side-to-side to head-to-foot. It is unknown what effect rocking orientation may have on sleep. AIM: This study aimed to investigate the impact of a simulated fore/aft orientation (side-to-side motion) with a simulated athwartships berth orientation (head-to-foot motion), on sleep quality and quantity, and cognitive performance. METHOD: 21 participants (13M/8F; 24.0±4.8 years; BMI 21.1±2.5) slept in berths on a motion platform replicating vessel motion. In a repeated measures design, each participant slept under three conditions in randomised order: 1) no motion, 2) fore/aft orientation (side-to-side motion), and 3) athwartships orientation (head-to-foot motion). Measurements of sleep (ambulatory polysomnography), sleepiness (Karolinska Sleepiness Scale: KSS), and vigilance (Psychomotor Vigilance Test: PVT) were analysed using Mixed Effects ANOVA. RESULTS: Participants’ total sleep time was shorter (p<0.001), sleep efficiency was reduced (p<0.001), they woke more frequently (p<0.001), and their sleep contained less REM (p<0.001) in the athwartships orientation (head-to-foot motion) compared to the no motion, and fore/aft orientation (side-to-side motion) conditions. Participants’ also reported significantly higher sleepiness on KSS (p=0.006), poorer subjective sleep quality (p<0.001), and displayed worse vigilant attention on PVT (p=0.03) following the athwartships orientation compared to the two other conditions. DISCUSSION: The simulated athwartships bunk orientation (head-to-foot motion) negatively impacted sleep and cognitive performance. These results may have implications for crew wellbeing. The data also gives unique theoretical insight into the effects of different types of rhythmic movement on sleep. FUNDING: DSTG