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Fatigue at Sea

Fatigue at Sea. Anna Dahlgren Reseracher, PhD Chalmers University of Technology Human Factors Shipping and Marine Technology Gothenburg, Sweden Phone: 0046(0)31 7726083 Email: anna.dahlgren@chalmers.se. Fatigue at sea. Introduction to mechanisms Countermeasures

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Fatigue at Sea

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  1. Fatigue at Sea Anna Dahlgren Reseracher, PhD Chalmers University of Technology Human Factors Shipping and Marine Technology Gothenburg, Sweden Phone: 0046(0)31 7726083 Email: anna.dahlgren@chalmers.se

  2. Fatigue at sea • Introduction to mechanisms • Countermeasures • Fatigue at sea – a field study • Horizon project – a simulator study

  3. At night – increased risk for injuries and accidents accident Traffic accidents Injuries during different shifts

  4. The circadian rhythm Effects on sleepiness and performance • Sleepiness shows a clear circadian rhythm during continuous wakefulness over several days • Sleepiness is greatest during late night and lowest during the afternoon. • Performance coincide very well with sleepiness and show a clear circadian rhythm. Åkerstedt & Gillberg

  5. The biological clock Pns

  6. Melatonin and body temperature Max performance, But disturbed sleep Low Performance Good Sleep

  7. Sleep length and time of day Sleep length

  8. The homeostatic process of sleep Fig. 1 The two-process model involving the circadian component (process C) and the homeostatic component (process S). Tonin and Cirelli, 2006

  9. The homeostatic process of sleep Tonin and Cirelli, 2006

  10. Decreased performance Longer reaction times Impaired attention Worse at planning ahead Impaired creativity Decreased vocabulary Become less able to express one self Learning and memory impairments Worse mood Performance degrades Increased accident risk Sleepiness – what happens?

  11. Effective Naps Coffee Modafinil Light Work Scheduling Moderate effect Cool, fresh air Radio Social activities Physical activity Snacking Te, coca cola Sudden noise Fatigue countermeasures

  12. Caffeine • Caffeine block adenosine receptors (stops/blocks homeostatic regulation of sleep) • Caffeine intake during night time or sleep deprivation:  micro sleep  cognitive performance • Caffeine can affect the following sleep episode (poor sleep quality & shorter sleep) • Combining nap (1-2h) and caffeine (300mg) before nightshifts reduces the decrements in performance (PVT) Beaumont et al., 2001; Lieberman et al., 2002; Wyatt et al., 2004; Schweitzer et al., 2006; Horne et al

  13. Modafinil • Act as a central stimulant • No side effects on the cardiovascular system or addiction • Is prescribed for Shift Work Sleep Disorder (SWSD) • Similar effect on sleepiness & performance as caffeine (Wesensten et al., 2002) • Shift workers with SWSD treated with modafinil showed during night shifts: • Objective & subjective sleepiness • Performance decrement • Increased insomnia (Czeisler et al, 2005)

  14. Light & Melatonin • Manipulate the circadian rhythm • Melatonin effectively promotes sleep and circadian adaption • No systematic research of the long term effects of melatonin intake • Bright light (2500 lux; indoor illumination is about 500 lux) can suppress the nocturnal secretion of melatonin delay sleep and entrain circadian rhythms (e.g. Eastman 1990) • Bright light needs to be scheduled according to work hours and circadian rhythm.

  15. The circadian rhythm light adjust the biological clock

  16. Bright light in shift workers Lowden et al., 2004 Bjorvatn et al., 1999

  17. Naps Can reduce the homeostatic drive for sleep Strategic napping: • Prophylactic naps: e.g. planned in evening before night shift • Recuperative naps: taken at night to temporarily relive sleepiness Individual differences Problem of sleep inertia?

  18. Nap reduce fatigueEEG measurements – compairison with flights with and without nap Mikro sleep Rosekind et al 1997

  19. Work scheduling – general guidelines for reducing fatigue • Limit the number of consecutive night shifts • Apply rapid rotation (1-3 shifts before changing) • Forward rotating (e.g. from morning shifts to afternoon) • Avoid quick returns • Avoid early morning shifts • Avoid shifts longer than 12 hours. (exponentially increase in accidents appears after 9 hours. (Hänecke et al., 1998) • Avoid long weekly work hours (>48h/week) • Number of rest days? – in proportion to amount of work • Predictable schedules and ability to influence There are no good shift schedules – only less bad ones Tucker & Folkard., 2010

  20. Rest breaks Tucker, P. Folkard, S. & Macdonald, I. (2003). Rest breaks and accident risk. The Lancet, 361, 680.

  21. Countermeasures - Summary The priority should be to create a sustainable work situation & environment • Work time scheduling • Rest breaks • Strategic napping • Light • Education and counseling programs • Psychosocial work environment (e.g. Stress, workload, control etc) • Physical work environment (e.g. Noise, temperature etc) • Work/life balance In cases of acute fatigue and sleepiness other countermeasures can be used. • Caffeine, modafinil • Unscheduled nap

  22. Fatigue at Sea • Long periods of sustained wakefulness (especially for coastal vessels) • Long work hours • Overtime work • Split shifts • Interrupted sleep • Extreme physical environment • Periods with either low activity and monotony or with high workload and demands Cheif Officer had had 2h of sleep in the past 37 hours

  23. Fatigue at Sea & Accidents • Fatigue was a contributing in 16% of critical vessel accidents and 33% of personal injuries (Raby & Lee., 2001) • 40.6% of nautical officers reported falling asleep at work and 17.6% during watch duties (Härmä et al., 2008) • Shift systems with 6 on 6 off have been shown to be overrepresented in accident reports (MAIB., 2004).

  24. Fatigue at sea – a field study • 13 Swedish cargo vessels • 6 on 6 off shift system and 4 on 8 off shift system • 15 participants on each shift schedule (tot=30) • Diary ratings (Karolinska Sleepiness Scale –KSS) • Eye movement behaviour (EOG) • Reaction Time Test • Objective sleep measures (actiwatch)

  25. Sleepiness during the watch • Sleepiness increased more during watch in the 6/6 system.

  26. Sleepiness & Sleep • Fatigue increased more during the night in the 6/6 system. Sleep in the 6/6 system: • More common with split sleep. • Each sleep episode tended to be shorter 3:15h vs. 3:43h (but no difference in total sleep length) Karolinska Sleepiuness Scale 1= very alert, 9=very sleepy, fighting sleep

  27. Sleepiness & extended work hours

  28. HORIZONFatigue and performance in watch keeping personell Margareta Lützhöft, Anna Dahlgren, Albert Kircher

  29. About the Horizon project • EU project with between several different partners and stakeholders • Financed with in the 7th framework. • The project stared in June 2009 and will go on for 30 months.

  30. Partners in HORIZON • Warsash Maritime Accademy Southampton Solent University • Stress Research Institute (Stockholm University) • Bureau Veritas Marine Division • European Community Shipowners' Associations • European Transport Workers' Federation • European Harbour Masters Committee • International Association of Independent Tanker Owners • Standard P&I Club • Marine Accident Investigation Branch • Maritime & Coastguard Agency

  31. Aim • Examine fatigue and performance in different watch keeping systems (6-6 and 4-8). We will also examine a third alternative watch schedule. • Develop a ”toolkit” for: - IMO - Flag states - Port States - Maritime Regulators - Ship Managers • Provide scientifically based recomendations to the industry and regluatory bodies wich will contribute to inceased safety at sea.

  32. Components of the model

  33. Procedure • Simulator experiment (5 bridge simulators and cargo handling simulators) • 1 week of driving in the simulator • 50 participants • 4 weeks spread out in 2010 • All participants will drive the same route in the English Channel.

  34. The balance between ”real life” and science

  35. Horizon Procedure • 1 week of driving in the simulator • All participants will drive the same route in the English Channel. Please do not tell the other watch teams what you have been doing in the simulator. • At one point during the week there will be overtime work and interruption of the free watch (balanced design)

  36. Measurements in HORIZON • Background questionnaire • Navigation in the simulator • Event judgment (rules, seamanship) • Diary ratings of fatigue, stress and workload. • Sleep.

  37. Measurements in HORIZON • EEG – brain activity • EOG – eye movement and blinks • ECG – heart • PVT – reaction time • KDT – Karolinska drowsiness test

  38. Lighthouse partner Thank you!

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