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A microsleep (MS) is a temporary episode of sleep which may last for a fraction of a second or up to thirty seconds where an individual fails to respond to some arbitrary sensory input and becomes unconscious.〔International Classification of Sleep Disorders Diagnostic and Coding Manual, http://www.esst.org/adds/ICSD.pdf, page 343〕〔Poudel, G. R., Innes, C. R., Bones, P. J., Watts, R., & Jones, R. D. (2012). Losing the struggle to stay awake: Divergent thalamic and cortical activity during microsleeps. Human Brain Mapping: 00:000-000〕 MSs occur when an individual loses awareness and subsequently gains awareness after a brief lapse in consciousness, or when there are sudden shifts between states of wakefulness and sleep. In behavioral terms, MSs manifest as droopy eyes, slow eyelid-closure, and head nodding.〔 In electrical terms, microsleeps are often classified as a shift in electroencephalography (EEG) during which 4–7 Hz (theta wave) activity replaces the waking 8–13 Hz (alpha wave) background rhythm. MSs often occur as a result of sleep deprivation, though normal non-sleep deprived individuals can also experience MSs during monotonous tasks.〔Chou, Y. H., Chuang, C. C., Zao, J. K., Ko, L. W., & Lin, C. T. (2011, August). An fMRI study of abrupt-awake episodes during behavioral microsleeps. In Engineering in Medicine and Biology Society, EMBC, 2011 Annual International Conference of the IEEE (pp. 5060-5063). IEEE.〕 Some experts define microsleep according to behavioral criteria (head nods, drooping eyelids, etc.), while others rely on EEG markers. Since there are many ways to detect MSs in a variety of contexts there is little agreement on how best to identify and classify microsleep episodes. Microsleeps become extremely dangerous when they occur in situations that demand constant alertness, such as driving a motor vehicle or working with heavy machinery. People who experience microsleeps usually remain unaware of them, instead believing themselves to have been awake the whole time, or to have temporarily lost focus. ==Background and significance== With over 1,550 fatalities and 40,000 nonfatal injuries occurring annually in the United States alone as a result of drowsy driving, sleep loss has become a public health problem.〔Insufficient Sleep Is a Public Health Epidemic. http://www.cdc.gov/features/dssleep/〕〔US Department of Transportation, National Highway Traffic Safety Administration, National Center on Sleep Disorders Research, National Heart Lung and Blood Institute. Drowsy driving and automobile crashes (Highway Traffic Safety Administration Web Site ). Available at http://www.nhtsa.gov/people/injury/drowsy_driving1/Drowsy.html#NCSDR/NHTSAExternal Web Site Icon Accessed February 10, 2011.〕 When experiencing microsleeps while driving an automobile, from the perspective of the driver, he or she drives a car, and then suddenly realizes that several seconds have passed by unnoticed. It is not obvious to the driver that he or she was asleep during those missing seconds, although this is in fact what happened. The sleeping driver is at very high risk for having an collision during a microsleep episode.〔(【引用サイトリンク】title=Microsleep )〕 Historically, many accidents and catastrophes have resulted from microsleep episodes in these circumstances. For example, a microsleep episode is claimed to have been one factor contributing to the Waterfall train disaster in 2003; the driver had a heart attack and the guard who should have reacted to the train's increasing speed is said by his defender to have microslept, thus causing him to be held unaccountable. On May 31, 2009, an Air France plane (Air France Flight 447) carrying 228 people from Brazil to France crashed into the Atlantic Ocean, killing everyone on board. The pilot of the plane reported "I didn't sleep enough last night. One hour – it's not enough," handing over control to the two co-pilots who did not respond appropriately when the plane was in distress.〔BEA final report, section 1.5, page 24 (PDF page 26 of 224): "The crew had left Paris on Thursday 28 May 2009 in the morning and arrived in Rio de Janeiro in the evening of the same day"〕〔"Revealed: Pilot of Air France jet that crashed in Atlantic Ocean killing 228 people had just ONE HOUR sleep before flight", ''The Daily Mail'' (UK), 2013-03-15.〕 Perhaps the most notable example was the Chernobyl nuclear reactor accident in the Ukraine in April, 1986. The reactor began to overheat at about 1:30am because critical cooling valves were shut off. The shiftworkers, sleep-deprived and likely experiencing microsleeps with consequent reduced decision-making ability, mistakenly disabled the cooling system, causing the reactor to overheat. As a result, there was a destructive explosion, resulting in numerous radiation-related injuries and casualties.〔Coren, Stanley. ''Sleep Thieves: An Eye-Opening Exploration into the Science & Mysteries of Sleep''. New York: The Free Press, 1996. p. x, 241–44〕 Thus, microsleeps are often examined in the context of driver drowsiness detection and prevention of work-related injuries and public safety incidents (e.g. truck crashes, locomotive crashes, airplane crashes, etc.). Some statistics are below: *44% of drivers during late-night driving become dangerously sleepy.〔Åkerstedt, T., Hallvig, D., Anund, A., Fors, C., Schwarz, J., & Kecklund, G. (2013). "Having to stop driving at night because of dangerous sleepiness–awareness, physiology and behaviour." ''Journal of Sleep Research''.〕 *Extremely fatiguing work protocols increase accident probability from near 0% to 35%.〔Sirois, B., Trutschel, U., Edwards, D., Sommer, D., & Golz, M. (2010, January). "Predicting Accident Probability from Frequency of Microsleep Events." In World Congress on Medical Physics and Biomedical Engineering, September 7–12, 2009, Munich, Germany (pp. 2284–2286). Springer Berlin Heidelberg.〕 *Chronic microsleeps (MSs) not only increase probability for injury but also decrease worker productivity and increase likelihood for absenteeism from work.〔Swanson, L. M., ARNEDT, J., Rosekind, M. R., Belenky, G., Balkin, T. J., & Drake, C. (2011). "Sleep disorders and work performance: findings from the 2008 National Sleep Foundation Sleep in America poll." ''Journal of Sleep Research'', 20(3), 487-494.〕 *According to one CDC (Centers for Disease Control and Prevention) study, among 74,571 adult respondents in 12 U.S. states, 35.3% reported <7 hours of sleep during a typical 24-hour period, 48.0% reported snoring, 37.9% reported unintentionally falling asleep during the day at least once in the preceding month, and 4.7% reported nodding off or falling asleep while driving at least once in the preceding month.〔 *The National Highway Traffic Safety Administration estimates that 2.5% of fatal crashes and 2% of injury crashes involve drowsy driving.〔National Highway Traffic Safety Administration. ''Traffic Safety Facts Crash Stats: Drowsy Driving''. Washington, DC: DOT; 2011. DOT HS 811 4492011.〕 *Fatigue is associated with 250 fatalities in air carrier accidents in last 16 years〔"Pilot fatigue is like 'having too much to drink'." CNN, May 15, 2009. http://www.cnn.com/2009/TRAVEL/05/15/pilot.fatigue.buffalo.crash/〕 However, most microsleeps are not dangerous. Microsleeps can be induced from monotonous tasks such as staring at a wall or listening to a boring lecture. In this context, these microsleeps are called daytime parahypnagogia (DPH) episodes, which can last for less than a second to a few seconds and often occur when the eyes are open.〔Gurstelle, E. B., & De Oliveira, J. L. (2004). "Daytime parahypnagogia: a state of consciousness that occurs when we almost fall asleep." ''Medical Hypotheses'', 62(2), 166–168.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「microsleep」の詳細全文を読む スポンサード リンク
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