Work at sea: a study of sleep, and of circadian rhythms in physiological and psychological functions, in watchkeepers on merchant vessels

Abstract

Sleep length and sleep quality scores were collected on board ships over periods of up to two weeks from 38 watchkeepers working a '4-on/8-off routine' and 29 dayworkers. All watchkeepers exhibited fragmented sleeping patterns, which indicated a lack of adaptation of the sleep/wakefulness cycle to the hours of work. There were only slight differences in total sleep length between watchkeepers and dayworkers, however, both groups did not obtain an adequate amount of sleep. Within the watchkeeping crews the 3rd Officers had by far the shortest sleep length. Concerning sleep quality, daytime sleep was generally given the lowest ratings, whereas sleep starting before midnight was on average evaluated as the best, both by watchkeepers and dayworkers. Watchkeeping personnel do not normally have any "days off" during a voyage so that missed sleep might even amount to a sleep deficit. A solution for this problem could perhaps be a new, stabilized system that allows a single uninterrupted sleep, which is required for full recuperation, to be taken each day.

Work hours, sleep patterns and fatigue among merchant marine personnel

“…In particular, the studies of Rutenfranz et al (1988) reported average sleep durations of 7.4 -7.5 h, nearly an hour greater than the 6.6 h obtained in the current study. Similarly, their average work durations were between 9.4 and 10.4 h, in distinction to the average of 11.5 h in the current study.…”

“…Rutenfranz et al (1988) also observed that personnel on the 04.00-08.00 watch were limited to a single sleep episode 20'% of the time. A similar percentage (22%) was obtained in this study; these sleep episodes resulted in less than 4 h of sleep in the 24-h period.…”

“…Sleep duration and quality in at-sea operations have been evaluated in several European studies, including Rutenfranz et al (1988) and Fletcher et al (1988). They found that watchkeepers had a lower average sleep duration than dayworkers, and that third officers (08.00-12.00 watch) reported the lowest quality and amount of sleep.…”

A systematic review of the sleep, sleepiness, and performance implications of limited wake shift work schedules

“…Only primary, peer-reviewed articles published in English were included, while studies examining pharmacological interventions were excluded. From this search, we identified 22 papers which examined LWSW (17)(18)(19)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40), two pairs of which overlap (25,29,36,37), leaving a total of 20 independent studies. The identified studies are summarized in table 1.…”

“…Eight of the studies identified in this review used a within-subject's design (18,22,23,25,29,(36)(37)(38), ten a between-subject's design (17,24,26,27,30,31,34,35,39,40), and four employed a mixed within-and between-subjects design (19,28,32,33). Seventeen studies were field-based (17-19, 22, 24-32, 34-37) and five used laboratory simulations (23,33,(38)(39)(40).…”