Fatigue from Sleep Loss and Circadian Misalignment: A Fatigue Risk Management Framework for Emergency Medical Services Hans P.A. Van Dongen, Ph.D. Director, Sleep and Performance Research Center Research Professor, Elson S. Floyd College of Medicine Washington State University Spokane Biological Clock and Circadian Rhythmicity photoreceptors retino- optic visual light in the retina hypothalamic nerve cortex (melanopsin) tract (inhibition) suprachiasmatic pineal nuclei (SCN) in gland the hypothalamus circadian rhythms melatonin and sleep Light input keeps the biological clock synchronized to external day and night Sleep/Wake Regulation: Timing and Duration • Longer periods of wakefulness cause greater pressure for sleep • Longer periods of sleep provide greater recovery from sleep pressure Ø Homeostatic process • There is greater pressure for sleep latency(min) at night than during the day • This is true even after sleep deprivation (“second wind”) Ø Circadian process time awake (h) • The homeostatic and circadian processes interact, as formalized in the two-process model of sleep regulation Borbély AA. Hum Neurobiol 1982, 1: 195-204. Dinges DF. Electroencephalogr Clin Neurophysiol 1986, 64: 224-227. Working Nights: Dual Sleep and Fatigue Challenge • The homeostatic drive for sleep homeostat builds up steadily over time awake • At the same time, the circadian → drive for wakefulness diminishes across the night and early morning Ø Thus, the two effects amplify each fatigue fatigue other, and cognitive performance circadian degrades across the work period Ø In addition, the circadian process restricts sleep duration during the 00 04 08 12 16 20 00 early evening, making it difficult to clock time (HH) get enough sleep Van Dongen HPA, Jackson ML, Raj S. MX Fatigue Focus 2010, 2(1): 7-9. Early Shift Start Case Study: MetroNorth Train Crash NY, Dec. 2013 need to start work go to bed wake up crash homeostatic drive for sleep ӿ → fatigue circadian drive for wakefulness 12 18 24 3006 3612 clock time (HH) Van Dongen, February 2016 Cumulative Fatigue from Chronic Sleep Restriction 0h TIB → → Subjectivesleepiness PVT lapses of attention PVT Graphs show daytime averages Van Dongen HPA, Maislin G, Mullington JM, Dinges DF. Sleep 2003, 26: 117-126. Duty Hours, Sleep/Wake Regulation and Fatigue Risk Management in EMS Settings countermeasures duty hours (timing & duration) light relative risk of ~ errors, incidents sleep inertia and accidents instability time on task fatigue (cognitive modulators in the impairment) environment weather, sea state, distractions, illness, • Neurobiological comes work demands, etc. with the individual (mostly transient) Satterfield BC, Van Dongen HPA. • Operational comes Fatigue Biomed Health Behav 2013, 1(3): 118-136. with the task at hand.