Papers by Wessel M A van Leeuwen
Sleep Medicine, Dec 1, 2017
Marine Policy, Jun 1, 2020
There is a substantial literature on fatigue among seafarers, but very little comparison of the e... more There is a substantial literature on fatigue among seafarers, but very little comparison of the experiences and perceptions of seafarers working for different companies and, in particular, those working for companies based in developed and developing countries. Using data from 880 questionnaires to seafarers and 60 interviews conducted with seafarers and managers, from two Chinese and two European shipping companies, this study takes a first step to addressing this gap. It reveals perceptions of higher fatigue, and poorer working and employment conditions, among seafarers working for Chinese as compared with European shipping companies. This difference was related to a relative lack of commitment from the Chinese shipping companies' managers to fatigue mitigation and a participatory approach. Overall, the findings suggest that although the merchant shipping industry has internationally regulated working and on-board living conditions, management practices and compliance standards within companies in different countries vary. International regulatory arrangements, therefore, do not result in a level playing fieldwhich has potentially serious consequences both for seafarers' safety, health and wellbeing, and for the safety of the world's fleets and marine environments. The findings also indicate that, despite differences in degree, fatigue continues to be a significant problem across the shipping industry. Finally, ways are suggested in which stakeholders could contribute to improving fatigue mitigation and management.
International Maritime Health, Jun 18, 2015
Background: The consequences of fatigue for the health and safety of seafarers has caused concern... more Background: The consequences of fatigue for the health and safety of seafarers has caused concern in the industry and among academics, and indicates the importance of further research into risk factors and preventive interventions at sea. This review gives an overview of the key issues relating to seafarer fatigue. Materials and methods: A literature study was conducted aiming to collect publications that address risk factors for fatigue, short-term and long-term consequences for health and safety, and options for fatigue mitigation at sea. Due to the limited number of publications that deals with seafarers, experiences from other populations sharing the same exposures (e.g. shift work) were also included when appropriate. Results: Work at sea involves multiple risk factors for fatigue, which in addition to acute effects (e.g., impaired cognition, accidents) contributes through autonomic, immunologic and metabolic pathways to the development of chronic diseases that are particularly prevalent in seafarers. Conclusions: Taking into account the frequency of seafarer fatigue and the severity of its consequences, one should look into the efficacy of the current legislative framework and the industry's compliance, the manning of the international merchant fleet, and optimised working, living and sleeping conditions at sea. Considering circumstances at sea, e.g. working in shifts and crossing time zones, that cannot be altered, further assessment of the potentials of preventive interventions including fatigue prediction tools and individual fatigue mitigation management systems is recommended.
VTI Rapport, 2015
Countermeasures for fatigue in transportation A review of existing methods for drivers on road, r... more Countermeasures for fatigue in transportation A review of existing methods for drivers on road, rail, sea and in aviation VTI rapport 852A | Countermeasures for fatigue in transportation-A review of existing methods for drivers on road, rail, sea and in aviation www.vti.se/publications VTI rapport 852A Published 2015 VTI rapport 852A
Marine Policy, Aug 1, 2021
Ships typically operate on a 24/7 basis giving rise to a wide variety of working time arrangement... more Ships typically operate on a 24/7 basis giving rise to a wide variety of working time arrangements and watch keeping schedules. Typically, these can be divided into 2-watch systems (where two watch keepers/teams share the 24-h period) and 3-watch systems (where three watch keepers/teams share the 24-h period). The current study uses the three-process model of alertness regulation to compare these systems in terms of the amount of severe sleepiness that is predicted to take place on watch and the amount of sleep that is predicted to occur while off watch. Separate predictions are calculated for individuals characterised as morning and evening chronotypes. Comparing 2-watch systems, highest levels of severe sleepiness were seen for evening types working 0000-1200 within the 12on12off system. The longest sleep per 24 h day was also found for evening types, but for those working the 1200-0000 watch within the 12on12off system. Total daily sleep duration ranged between 268 and 445 min. However, the picture is complex and the lowest risk of severe sleepiness while on watch is not necessarily correlated with the maximal time available for rest and recuperation when off watch. For 3-watch systems, the "five-and-dime" system (changeover times: 02-07-12-17-22) stands out having the lowest prevalence of severe sleepiness on watch and the longest amount of predicted daily sleep off watch. Considerable differences exist between morning and evening types offering the opportunity for considerable improvement in sleep amount for fixed (but not rotating) systems when individual chronotype is considered in watch scheduling. It is concluded that 3-watch systems, although economically costlier, have clear advantages over 2-watch systems, but that a perfect system that fits all does not exist due to the considerable impact of individual differences related to sleep/wake regulation.
Journal of Clinical and Experimental Neuropsychology, Aug 1, 2005
Recently a novel interference task was developed, that was aimed at obtaining robust patterns of ... more Recently a novel interference task was developed, that was aimed at obtaining robust patterns of interference in individual subjects, both behaviorally and neurophysiologically (Bush, Shin, Holmes, Rosen & Vogt, 2003). This multi-source interference task (MSIT) combined elements of spatial and flanker interference, and huge interference effects were obtained in a blocked design. This task could thus in principle be used to assess frontal abnormalities, such as ADHD. In the present study, we further examined the nature of the MSIT. We examined the effect of randomization, and the relative contribution of each type of interference. Using a group of healthy subjects, we found a much smaller interference effect than Bush et al. (2003). In addition, we found that most of the interference could be ascribed to flanker interference, and much less to spatial interference. It seems to be the case that there is a trade-off between obtaining robust and reliable effects, and isolating a specific psychological process.
Translational Psychiatry, Mar 20, 2012
Epidemiological studies show association between sleep duration and lipid metabolism. In addition... more Epidemiological studies show association between sleep duration and lipid metabolism. In addition, inactivation of circadian genes induces insulin resistance and hyperlipidemia. We hypothesized that sleep length and lipid metabolism are partially controlled by the same genes. We studied the association of total sleep time (TST) with 60 genetic variants that had previously been associated with lipids. The analyses were performed in a Finnish population-based sample (N ¼ 6334) and replicated in 2189 twins. Finally, RNA expression from mononuclear leucocytes was measured in 10 healthy volunteers before and after sleep restriction. The genetic analysis identified two variants near TRIB1 gene that independently contributed to both blood lipid levels and to TST (rs17321515, P ¼ 8.92*10 À5 , Bonferroni corrected P ¼ 0.0053, b ¼ 0.081 h per allele; rs2954029, P ¼ 0.00025, corrected P ¼ 0.015, b ¼ 0.076; Po0.001 for both variants after adjusting for blood lipid levels or body mass index). The finding was replicated in the twin sample (rs17321515, P ¼ 0.022, b ¼ 0.063; meta-analysis of both samples P ¼ 8.1*10 À6 , b ¼ 0.073). After the experimentally induced sleep restriction period TRIB1 expression increased 1.6-fold and decreased in recovery phase (P ¼ 0.006). In addition, a negative correlation between TRIB1 expression and slow wave sleep was observed in recovery from sleep restriction. These results show that allelic variants of TRIB1 are independently involved in regulation of lipid metabolism and sleep. The findings give evidence for the pleiotropic nature of TRIB1 and may reflect the shared roots of sleep and metabolism. The shared genetic background may at least partially explain the mechanism behind the well-established connection between diseases with disrupted metabolism and sleep.
International Maritime Health
Background: This study investigates how Faroese deep-sea fishers' exposure to work-related stress... more Background: This study investigates how Faroese deep-sea fishers' exposure to work-related stressors affects their sleep, sleepiness, and levels of fatigue. Being constantly exposed to the unpredictable and harsh North Atlantic Ocean, having long work hours and split sleep for up to 40 days consecutively, they will arguably suffer from fatigue. Materials and methods: One hundred and fifty seven fishers participated in this study, and data was gathered throughout 202 days at sea. Subjective data was collected at the start and end of trips via questionnaires, sleep and sleepiness diaries and supplemented by objective sleep data through actigraphs. Ship movements were logged with a gyroscope connected to a laptop. A noise metre measured each work station and resting area, and noise exposure profiles were calculated based on each participant's activity and location. Linear mixed-effect models investigated the effects of work exposure variables on sleep efficiency, and cumulative link mixed models measured effects on the Karolinska Sleepiness Scale and physical fatigue scale. Results: Time of day followed by ship movement were the exposure variables with the highest impact on the outcome variables of sleep efficiency, sleepiness and physical fatigue. The number of days at sea revealed correlations to outcome variables either by itself or interacting with the sleep periods per day. Crew size, shift system or noise did not impact outcome variables when in the model with other variables. Larger catches improved sleep efficiency but did not affect sleepiness and physical fatigue ratings. Conclusions: The findings indicate a chronically fatigued fisher population, and recommends urgent attention being paid to improving the structure of vessels and installing stabilators for greater stability at sea; work schedules being evaluated for protection of health; and work environments being designed that fulfill human physiological requirements in order to ensure the wellbeing and safety of those at sea.
Springer eBooks, 2017
The consequences of fatigue for the health and safety of seafarers have caused concern in the ind... more The consequences of fatigue for the health and safety of seafarers have caused concern in the industry and among academics, and indicates the importance of further research into risk factors and preventive interventions at sea. This chapter gives an overview of the key issues relating to seafarer fatigue. A literature study was conducted aimed at collecting publications that address risk factors for fatigue, short-term and long-term consequences for health and safety, and options for fatigue mitigation at sea. Due to the limited number of publications that deal with seafarers, experiences from other populations sharing the same exposures (e.g. shift work) were also included when appropriate. Work at sea involves multiple risk factors for fatigue, which in addition to acute effects (e.g. impaired cognition, accidents) contributes through autonomic, immunologic and metabolic pathways to the development of chronic diseases that are particularly prevalent in seafarers. Taking into account the frequency of seafarer fatigue and the severity of its consequences, the efficacy of the current legislative framework and the industry’s compliance, the manning of the international merchant fleet, and optimized working, living and sleeping conditions at sea all need serious reconsideration. Given the circumstances at sea which cannot be altered, e.g. working in shifts and crossing time zones, further assessment of the potentials of preventive interventions including fatigue prediction tools and individual Fatigue Risk Management Systems (FRMS) is recommended.
22nd Congress of the European Sleep Research Society, 16-20 September 2014, Tallinn, Estonia, 2014
Recently a novel interference task was developed, that was aimed at obtaining robust patterns of ... more Recently a novel interference task was developed, that was aimed at obtaining robust patterns of interference in individual subjects, both behaviorally and neurophysiologi-cally (Bush, Shin, Holmes, Rosen & Vogt, 2003). This multi-source interference task (MSIT) combined elements of spatial and flanker interference, and huge interference effects were obtained in a blocked design. This task could thus in principle be used to assess frontal abnormalities, such as ADHD. In the present study, we further examined the nature of the MSIT. We examined the effect of randomization, and the relative con-tribution of each type of interference. Using a group of healthy subjects, we found a much smaller interference effect than Bush et al. (2003). In addition, we found that most of the interference could be ascribed to flanker interference, and much less to spatial interference. It seems to be the case that there is a trade-off between obtaining robust and reliable effects, and isolating a specif...
Copyright © 2010 Wessel M. A. van Leeuwen et al. This is an open access article distributed under... more Copyright © 2010 Wessel M. A. van Leeuwen et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. This study identifies the effects of sleep restriction and subsequent recovery sleep on glucose homeostasis, serum leptin levels, and feelings of subjective satiety. Twenty-three healthy young men were allocated to a control group (CON) or an experimental (EXP)
Nature and Science of Sleep, 2022
Faroese fishers have four times more accidents than workers on land. The aim was to understand fi... more Faroese fishers have four times more accidents than workers on land. The aim was to understand fishers' fatigue better and how their work and sleep patterns influenced their sleepiness levels and cognitive performance. Materials and Methods: A total of 157 Faroese fishers wore wrist-worn actigraphs at sea and one week on land and filled in sleep and sleepiness diaries during the trip. Furthermore, a 3-minute simple reaction time (SRT) test was completed at the beginning and end of the trip. The ship's movement and noise were also logged. The actiwatch results were analysed with mixed methods repeated measures. The sleepiness registrations and performance on the SRT-test were analysed with paired t-test. The ship movements (Pitch and roll) were divided into approximately three same-sized groups (lowest 1/3, medium 1/3, and highest 1/3) and compared against the Karolinska Sleepiness Scores (KSS ranging from 1-9) ≥7 and physical tiredness (ranging from 1-9) scores ≥7. Chi-square tests were used to determine the significance of these differences. Mean sleepiness scores at sea, and the proportion of sleepiness scores ≥7 were calculated, as well as sleepiness scores as a function of the time of day. Results: While at sea, fishers had more split sleep, slept less, and had lower sleep efficiency than onshore. Sleepiness was higher at the end of the trip, and cognitive decline was found. The number of major lapses was higher at the end of the trip, but with no significant difference between the median reaction times. Conclusion: The crew on-board the freezer longliner, who worked 8-8 shifts, slept the most, had the longest continuous sleep periods, the highest sleep efficiency, the lowest sleepiness levels, and the highest noise exposure during their time off.
The aim of the study was to explore the levels of sleepiness and the psychosocial issues associat... more The aim of the study was to explore the levels of sleepiness and the psychosocial issues associated with long term fatigue and motivation, using a sample of volunteer seafarers in the naturalistic setting of work onboard their vessels.
Simulators for Transportation Human Factors, 2017
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Papers by Wessel M A van Leeuwen