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Sleep and Sleep-Wake rhythmicity: impact on (shift) work d r. Gerard A. Kerkhof , prof. em . University of Amsterdam & MCH Sleep Center, The Hague. Seminar ‘Safety in Seafisheries’ – Oct 3, 2013. Edison’s prophesy: “Artificial light frees us from the night”
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Sleep and Sleep-Wake rhythmicity: impact on (shift) work dr. Gerard A. Kerkhof, prof. em. University of Amsterdam & MCH Sleep Center, The Hague Seminar ‘Safety in Seafisheries’ – Oct 3, 2013
Edison’s prophesy: • “Artificial light frees us from the night” • “Shift work”: work outside the hours • 7 a.m. - 7 p.m. Kerkhof GA (2013), in preparation.
A day (and night) in the life of 18-24 yr adolescents: % mobile text traffic over 24 hours Yesterday newspaper (Volkskrant): Day and night young people are busy with their mobile: ‘Socialbesitas’?
Shift work increases the risk of a sleep disorder • Risks: • Accidents • Illness (Kerkhof GA, in preparation, 2013)
‘Fatigue’ is often synonymous with ‘Sleepiness’ (“Are you also so tired?”)
Crash Airbus, Tripoli May 12, 2010, 06:01a.m. Risk analysis: ‘Swiss cheese model’ (holes = risks) Fail-Safe Accident • Accumulation of: • Miscommunication (captain & co-pilot& Tower) • Unexpected poor visibility (fog patches) • No Instrument Landing System • No evaluation of landing errors 2 wk earlier • Fatigue (2nd night shift, early morning) • Conclusion: ‘Pilot error’ (i.e. Fatigue)
Disasters during the night Three Mile Island, U.S.A., 03.28.1979, 4 a.m. Chernobyl, Russia, 04.26.1986, 1.30 a.m. Exxon Valdez, Alaska 03.24.1989, 1 a.m. Bhopal, India, 12.03.1984, 1 a.m.
Rate of work injury per 200,000 h worked (Ontario, 2004 – 2008; N=707933) (Mustard et al, Occup Environ Med, 2013)
Health risks of shiftwork • Sleep disorder • Fatigue (chronic) • Cognitive disfunctioning: • errors in perception, • concentration, memory, • decision making, etc. • Emotional disregulation • Irritability • Anxiety • Cardiovascular disease • Increased cholesterol level • Hypertension • Impaired motor • coordination and • accuracy • Impaired motor coordination and precision • Disrupted immune • system • In addition: • Breast cancer • Growth suppression • Alzheimer’s disease • Other: • Growth suppression • Risk of Alzheimer’s • disease • Insuline resistance • Obesity • Diabetes type 2 • Gastro-intestinal • disease “Metabolic syndrome”
Biological Clock Shift work Sleep Family
Circadian pacemaker Suprachiasmatic nuclei Cross section of brain Nerve impulses 3rdventrikel Chiasma Network of Clock genes
The Biological Clock is tuned to the day/night cycle Michel Siffre, 1962 Sleep periods 00 12 24 h Freerunning Synchronized
The Biological Clock conducts an orchestra of 24-h rhythms Sleep
One sailor, one boat, one ocean May 25th 2009: start Plymouth, UK Newport, USA appr. 3000 miles, 5 time zones UK USA
Activity recording of solo sailor Start • Mean sleep duration/24h: 6.5 h, • 2 hours less than baseline • 46% sleep/8h dark (baseline: 73%) • Sleep bouts: mean 12’ • Periodogram analysis: • 24h amplitude • equivalent peaks: 13h, 17h Finish Plot of wrist activity (black) superimposed upon plot of daylight (yellow), from the start in Plymouth UK until the finish in Newport USA. Time axis: clock time in NL.
Two processes for Fatigue modeling 2. Sleep process 1. Circadian process 3. Sum Sleep Sleep 08 16 24 08 16 24 08 Time of Day (h) (GA Kerkhof, 2013)
One night sleep deprivation increases the sleep process Sleep process Circadian process Sum Wake Sleep 08 16 24 08 16 24 08 Time of Day (h) (GA Kerkhof, 2013)
Long distance coach driving Ride Ride Sleep cabin Activity monitor (KerkhofGA et al. 2003)
Risk of accidents increases over successive nights Night Day (Folkard & Tucker, 2003)
Biological Clock Shift work Sleep Family
Sleep duration for different shifts work sleep Night shift Early shift ↔ ↔ Late shift 18 22 02 06 10 14 18 Time of Day (h) (Knauth & Rutenfranz, 1981)
Hypnogram: sleep stages REM-sleep Deepsleep Electroencephalogram
Sleep: period of recovery and consolidation REM-sleep Deep sleep Growth hormone Prolactin
Day sleep differs from Night sleep Wake 1/REM 2 3 4 Wake 1/REM 2 3 4 18 22 02 06 10 14 18 Time of Day (h)
Daily averages of number of PVT lapses over two successive weeks of sleep restriction (N = 36) TIB: 4h 6h 8h Psychomotor Vigilance Test Successive days of sleep restriction (Van Dongen et al, 2003)
With increasing sleep deficit performance becomes more unstable and unpredictable 10 min Psychomotor Vigilance Test (PVT) Doran SM, Van Dongen HPA, Dinges DF (2001). Sustained attention performance during sleep deprivation: Evidence of state instability. Archives of Italian Biology 139: 253-267.
Variability of lapses at night Meetmomenten Measurements (Kerkhof GA & Hofman P, 2010)
Individual differences in vulnerability to sleep loss • Subjective sleepiness is unreliable indicator of impact Lapses of attention Subjective sleepiness n=7 n=8 Van Dongen HPA, Maislin G, Dinges DF (2004). Dealing with inter-individual differences in the temporal dynamics of fatigue and performance: Importance and techniques. Aviation, Space, and Environmental Medicine 75(3, Section II): A147-A154.
Individual Differences in Vulnerability to Sleep Loss in Active-Duty F-117A (Night Hawk) Fighter Pilots left 720 degrees turn roll angle performance flight path deviation 38-hour extended mission time relative performance (Self-)selection mechanisms do not eliminate individual differences in vulnerability to sleep loss N=10 Van Dongen HPA, Caldwell JA Jr, Caldwell JL. Investigating systematic individual differences in sleep-deprived performance on a high-fidelity flight simulator. Behavior Research Methods, 2006; 38(2): 333–343. pilots
Fatigue/Sleepiness is a major risk factor and sum of • a circadian rhythm with its maximum at night, and • a sleep process that increases as a function of time • awake • The vulnerability to sleep loss is an individual trait • Subjective sleepiness is an unreliable predictor of the risks of sleep loss • Sleep loss induces impaired and unpredictable performance • Shift work increases health risks • Consider preventive measures Recap