Changes in higher order cognitive function between four watch keeping schedules.

ABSTRACT

Maritime industries utilize many different watch keeping schedules to maintain vigilance and crew safety around the clock. These schedules can be fatiguing, negatively impacting vigilant attention. This has led to the consideration of schedules that might allow for more sleep time, but how these schedules impact higher order cognitive function remains unclear. These schedules require assessment with tasks that are relevant to real-world operations on maritime vessels. This study investigated the effect of four schedules on higher order cognitive function. N = 27 (16 female) participants were recruited to a 10-day laboratory study, comparing four schedules. The schedules investigated were eight-on/eight-off/four-on/four-off (8/8/4/4) with sleep from 0930 to 1600 (condition A); six-on/six-off (6/6) with sleep from 0830 to 1230 and 2130 to 0000 (condition B); four-on/four-off (4/4/4/4/4/4) with sleep from 1800 to 0030 (condition C); and four-on/four-off (4/4/4/4/4/4) with sleep from 0130 to 0800 (condition D). Higher order cognitive function was assessed 2-3× daily whilst "on watch" using tests of visual scanning, learning, working memory, mental flexibility, and visuomotor control. Conditions were ranked and stability of performance on watch was compared between conditions using Kruskal-Wallis tests. Cognitive function within condition B was ranked the worst for most of the tasks. However, the stability of higher order cognitive function was poorest across the waking day within condition A. These findings highlight the variability in cognitive capacities during different watch keeping schedules.