Wessel is course leader for the master course Stress, recovery and health (7,5 hp) within the master programme Population health: Societal and individual perspectives at the Department of Public Health Sciences.

A selection from Stockholm University publication database

• Sleep in everyday life – relationship to mood and performance in young and older adults: a study protocol

  2023. Johanna F. A. Schwarz (et al.). Frontiers in Psychology 14

  Article

  Laboratory based sleep deprivation studies demonstrate that lack of sleep impairs well-being and performance ability, but suggest that these effects are mitigated in older adults. Yet, much less is known whether day-to-day variations of sleep have similar consequences in the context of everyday life. This project uses an intensive longitudinal design to investigate the occurrence of day-to-day variations in sleep and their impact on mood and performance in everyday life and to examine whether effects differ between young and older adults. We aim to include 160 young (18–30 years) and 160 older adults (55–75 years) to complete a 21-day experience sampling method (ESM) protocol. During the ESM period, participants are asked to fill in (i) a brief morning questionnaire, (ii) 8 short daytime questionnaires addressing momentary well-being, sleepiness, stress, and mind wandering, followed by a 1 min cognitive task and (iii) a brief evening questionnaire, all delivered via a mobile phone application. Sleep will be measured using self-reports (daily questions) and objectively with wrist actigraphy. The impact of adult age on mean levels and intraindividual variability of sleep will be analyzed using mixed-effects location scale models. The impact of sleep on daily cognitive performance will be analyzed using multilevel linear mixed models. The relationship of sleep to mean values and variability of positive and negative affect in young and older adults will be analyzed using mixed-effects location scale modeling. The overarching purpose of the project is improving the current knowledge on the occurrence of day-to-day variations in sleep and their relationship to performance as well as positive and negative affect in young and older adults.

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• Working environment and fatigue among fishers in the north Atlantic: a field study

  2023. Annbjørg Selma Abrahamsen (et al.). International Maritime Health 74 (1), 1-14

  Article

  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.

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• Impact of work exposure on cognitive performance in Faroese deep-sea fishers: a field study

  2022. Annbjørg Selma Abrahamsen (et al.). International Maritime Health 73 (3), 150-161

  Article

  Background: This study examines the impact of work-related exposure on the cognitive performance of Faroese deep-sea fishers. Faroese fishing crews work long hours in demanding and noisy environments amidst highly uncertain and challenging weather conditions. These factors, together with compromised patterns of rest and sleep, are known to increase fatigue. Our aim was to study if changes could be measured in fishers’ cognitive performance at the end of the trip when compared with the baseline measure at the beginning.

  Materials and methods: Data was collected over 15 months (May 2017 to July 2018) from 157 fishers on 18 fishing trips which involved 202 investigative days on board. Questionnaires and six computerised cognitive tests: Simple Reaction Time, Numeric Working Memory, Corsi Blocks, Rapid Visual Information Processing, Digit Vigilance, and Card Sorting Test were used for data collection at the beginning and end of the trip. Differences between the outcomes on the two test points were analysed with one-way ANOVA comparing the performances at the beginning and end of the voyage, and two-way ANOVA to examine the interactive effect of chronotype and test occasions on the outcomes. Mixed models were used to test for the effects of predictor variables.

  Results: Significant declines in cognitive performance were observed from the beginning to the end of the trip, with decreases in visuospatial memory and reaction times, and increases in cognitive lapses. Furthermore, slowing in response times was observed in the second half of the Digit Vigilance test when comparing the halves.

  Conclusions: Declines in performance were observed from the start to the end of the trip. Furthermore, fishers performed significantly worse in the second half of some parted tests, and evening types seem less influenced by irregular work hours. These findings call for improving the safety of the vessels and their crew.

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• Sleep, Sleepiness, and Fatigue on Board Faroese Fishing Vessels

  2022. Annbjørg Abrahamsen (et al.). Nature and Science of Sleep 14, 347-362

  Article

  Purpose: 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.

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• Mathematical modelling of sleep and sleepiness under various watch keeping schedules in the maritime industry

  2021. Wessel M. A. van Leeuwen (et al.). Marine Policy 130

  Article

  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.

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• Real-Time Adaptation of Driving Time and Rest Periods in Automated Long-Haul Trucking

  2021. Christer Ahlström (et al.). IEEE transactions on intelligent transportation systems (Print)

  Article

  Hours of service regulations govern the working hours of commercial motor vehicle drivers, but these regulations may become more flexible as highly automated vehicles have the potential to afford periods of in-cab rest or even sleep while the vehicle is moving. A prerequisite is robust continuous monitoring of when the driver is resting (to account for reduced time on task) or sleeping (to account for the reduced physiological drive to sleep). The overall aims of this paper are to raise a discussion of whether it is possible to obtain successful rest during automated driving, and to present initial work on a hypothetical data driven algorithm aimed to estimate if it is possible to gain driving time after resting under fully automated driving. The presented algorithm consists of four central components, a heart rate-based relaxation detection algorithm, a camera-based sleep detection algorithm, a fatigue modelling component taking time awake, time of day and time on task into account, and a component that estimates gained driving time. Real-time assessment of driver fitness is complicated, especially when it comes to the recuperative value of in-cab sleep and rest, as it depends on sleep quality, time of day, homeostatic sleep pressure and on the activities that are carried out while resting. The monotony that characterizes for long-haul truck driving is clearly interrupted for a while, but the long-term consequences of extended driving times, including user acceptance of the key stakeholders, requires further research.

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• Comparison of perceived fatigue levels of seafarers and management approaches in fatigue mitigation

  2020. Zhiwei Zhao (et al.). Marine Policy 116

  Article

  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 field - which 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.

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• Physiological and autonomic stress responses after prolonged sleep restriction and subsequent recovery sleep in healthy young men

  2018. Wessel M. A. van Leeuwen (et al.). Sleep and Biological Rhythms 16 (1), 45-54

  Article

  Purpose

  Sleep restriction is increasingly common and associated with the development of health problems. We investigated how the neuroendocrine stress systems respond to prolonged sleep restriction and subsequent recovery sleep in healthy young men.

  Methods

  After two baseline (BL) nights of 8 h time in bed (TIB), TIB was restricted to 4 h per night for five nights (sleep restriction, SR, n = 15), followed by three recovery nights (REC) of 8 h TIB, representing a busy workweek and a recovery weekend. The control group (n = 8) had 8 h TIB throughout the experiment. A variety of autonomic cardiovascular parameters, together with salivary neuropeptide Y (NPY) and cortisol levels, were assessed.

  Results

  In the control group, none of the parameters changed. In the experimental group, heart rate increased from 60 ± 1.8 beats per minute (bpm) at BL, to 63 ± 1.1 bpm after SR and further to 65 ± 1.8 bpm after REC. In addition, whole day low-frequency to-high frequency (LF/HF) power ratio of heart rate variability increased from 4.6 ± 0.4 at BL to 6.0 ± 0.6 after SR. Other parameters, including salivary NPY and cortisol levels, remained unaffected.

  Conclusions

  Increased heart rate and LF/HF power ratio are early signs of an increased sympathetic activity after prolonged sleep restriction. To reliably interpret the clinical significance of these early signs of physiological stress, a follow-up study would be needed to evaluate if the stress responses escalate and lead to more unfavourable reactions, such as elevated blood pressure and a subsequent elevated risk for cardiovascular health problems.

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• Does sleep deprivation increase the vulnerability to acute psychosocial stress in young and older adults?

  2018. Johanna Schwarz (et al.). Psychoneuroendocrinology 96, 155-165

  Article

  Sleep loss and psychosocial stress often co-occur in today’s society, but there is limited knowledge on the combined effects. Therefore, this experimental study investigated whether one night of sleep deprivation affects the response to a psychosocial challenge. A second aim was to examine if older adults, who may be less affected by both sleep deprivation and stress, react differently than young adults. 124 young (18–30 years) and 94 older (60–72 years) healthy adults participated in one of four conditions: i. normal night sleep & Placebo-Trier Social Stress Test (TSST), ii. normal night sleep & Trier Social Stress Test, iii. sleep deprivation & Placebo-TSST, iv. sleep deprivation & TSST. Subjective stress ratings, heart rate variability (HRV), salivary alpha amylase (sAA) and cortisol were measured throughout the protocol. At the baseline pre-stress measurement, salivary cortisol and subjective stress values were higher in sleep deprived than in rested participants. However, the reactivity to and recovery from the TSST was not significantly different after sleep deprivation for any of the outcome measures. Older adults showed higher subjective stress, higher sAA and lower HRV at baseline, indicating increased basal autonomic activity. Cortisol trajectories and HRV slightly differed in older adults compared with younger adults (regardless of the TSST). Moreover, age did not moderate the effect of sleep deprivation. Taken together, the results show increased stress levels after sleep deprivation, but do not confirm the assumption that one night of sleep deprivation increases the responsivity to an acute psychosocial challenge.

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• Risk Factors for Fatigue in Shipping, the Consequences for Seafarers’ Health and Options for Preventive Intervention

  2017. Jørgen Riis Jepsen (et al.). Maritime Psychology, 127-150

  Chapter

  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.

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• Maritime research

  2017. Margareta Lutzhoft (et al.). Simulators for Transportation Human Factors

  Chapter

  Simulation continues to be a growth area in transportation human factors. From empirical studies in the laboratory to the latest training techniques in the field, simulators offer myriad benefits for the experimenter and the practitioner. This book draws together current trends in research and training simulators for the road, rail, air and sea sectors to inform the reader how to maximize both validity and cost-effectiveness in each case. Simulators for Transportation Human Factors provides a valuable resource for both researchers and practitioners in transportation human factors on the use of simulators, giving readers concrete examples and case studies of how simulators have been developed and used in empirical research as well as training applications. It offers useful and usable information on the functional requirements of simulators without the need for any background knowledge on the technical aspects, focusing on the state of the art of research and applications in transport simulators rather than the state of the art of simulation technology. The book covers simulators in operational terms instead of task simulation/modelling and provides a useful balance between a bottom-up, academic approach and a top-down, practical perspective.

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Show all publications by Wessel van Leeuwen at Stockholm University