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Sleep, sleepiness, and neurobehavioral performance while on watch in a simulated 4 hours on/8 hours off maritime watch system


van Leeuwen, WMA and Kircher, A and Dahlgren, A and Lutzhoft, MH and Barnett, M and Kecklund, G and Akerstedt, T, Sleep, sleepiness, and neurobehavioral performance while on watch in a simulated 4 hours on/8 hours off maritime watch system, Chronobiology International, 30, (9) pp. 1108-1115. ISSN 1525-6073 (2013) [Refereed Article]

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Copyright 2013 Informa Healthcare USA, Inc.

DOI: doi:10.3109/07420528.2013.800874


Seafarer sleepiness jeopardizes safety at sea and has been documented as a direct or contributing factor in many maritime accidents. This study investigates sleep, sleepiness, and neurobehavioral performance in a simulated 4 h on/8 h off watch system as well as the effects of a single free watch disturbance, simulating a condition of overtime work, resulting in 16 h of work in a row and a missed sleep opportunity. Thirty bridge officers (age 30 ± 6 yrs; 29 men) participated in bridge simulator trials on an identical 1-wk voyage in the North Sea and English Channel. The three watch teams started respectively with the 00–04, the 04–08, and the 08–12 watches. Participants rated their sleepiness every hour (Karolinska Sleepiness Scale [KSS]) and carried out a 5-min psychomotor vigilance test (PVT) test at the start and end of every watch. Polysomnography (PSG) was recorded during 6 watches in the first and the second half of the week. KSS was higher during the first (mean ± SD: 4.0 ± 0.2) compared with the second (3.3 ± 0.2) watch of the day (p < 0.001). In addition, it increased with hours on watch (p < 0.001), peaking at the end of watch (4.1 ± 0.2). The free watch disturbance increased KSS profoundly (p < 0.001): from 4.2 ± 0.2 to 6.5 ± 0.3. PVT reaction times were slower during the first (290 ± 6 ms) compared with the second (280 ± 6 ms) watch of the day (p < 0.001) as well as at the end of the watch (289 ± 6 ms) compared with the start (281 ± 6 ms; p = 0.001). The free watch disturbance increased reaction times (p < 0.001) from 283 ± 5 to 306 ± 7 ms. Similar effects were observed for PVT lapses. One third of all participants slept during at least one of the PSG watches. Sleep on watch was most abundant in the team working 00–04 and it increased following the free watch disturbance. This study reveals that—within a 4 h on/8 h off shift system—subjective and objective sleepiness peak during the night and early morning watches, coinciding with a time frame in which relatively many maritime accidents occur. In addition, we showed that overtime work strongly increases sleepiness. Finally, a striking amount of participants fell asleep while on duty.

Item Details

Item Type:Refereed Article
Keywords:bridge simulator, fatigue, KSS, overtime work, polysomnography, psychomotor vigilance test, seafarers
Research Division:Psychology
Research Group:Cognitive and computational psychology
Research Field:Sensory processes, perception and performance
Objective Division:Transport
Objective Group:Water transport
Objective Field:Water safety
UTAS Author:Lutzhoft, MH (Professor Margareta Lutzhoft)
ID Code:88081
Year Published:2013
Web of Science® Times Cited:21
Deposited By:NC Ports and Shipping
Deposited On:2014-01-10
Last Modified:2017-11-03

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