Microsleep
Encyclopedia
A microsleep is an episode of sleep
which may last for a fraction of a second or up to thirty seconds. Often, it is the result of sleep deprivation
, mental fatigue
, depression, sleep apnea
, hypoxia
, narcolepsy
, or hypersomnia
. For the sleep-deprived, microsleeping can occur at any time, typically without substantial warning.
Microsleeps (or microsleep episodes) become extremely dangerous when they occur in situations which 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.
There is little agreement on how best to identify microsleep episodes. Some experts define microsleep according to behavioral criteria (head nods, drooping eyelids, etc.), while others rely on EEG
markers. One study at the University of Iowa
defined EEG-monitored microsleeps in driving simulation as "a 3–14 second episode during which 4–7 Hz (theta) activity replaced the waking 8–13 Hz (alpha) background rhythm."
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 accident during a microsleep episode.
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.
Sleep
Sleep is a naturally recurring state characterized by reduced or absent consciousness, relatively suspended sensory activity, and inactivity of nearly all voluntary muscles. It is distinguished from quiet wakefulness by a decreased ability to react to stimuli, and is more easily reversible than...
which may last for a fraction of a second or up to thirty seconds. Often, it is the result of sleep deprivation
Sleep deprivation
Sleep deprivation is the condition of not having enough sleep; it can be either chronic or acute. A chronic sleep-restricted state can cause fatigue, daytime sleepiness, clumsiness and weight loss or weight gain. It adversely affects the brain and cognitive function. Few studies have compared the...
, mental fatigue
Fatigue (physical)
Fatigue is a state of awareness describing a range of afflictions, usually associated with physical and/or mental weakness, though varying from a general state of lethargy to a specific work-induced burning sensation within one's muscles...
, depression, sleep apnea
Sleep apnea
Sleep apnea is a sleep disorder characterized by abnormal pauses in breathing or instances of abnormally low breathing, during sleep. Each pause in breathing, called an apnea, can last from a few seconds to minutes, and may occur 5 to 30 times or more an hour. Similarly, each abnormally low...
, hypoxia
Hypoxia (medical)
Hypoxia, or hypoxiation, is a pathological condition in which the body as a whole or a region of the body is deprived of adequate oxygen supply. Variations in arterial oxygen concentrations can be part of the normal physiology, for example, during strenuous physical exercise...
, narcolepsy
Narcolepsy
Narcolepsy is a chronic sleep disorder, or dyssomnia, characterized by excessive sleepiness and sleep attacks at inappropriate times, such as while at work. People with narcolepsy often experience disturbed nocturnal sleep and an abnormal daytime sleep pattern, which often is confused with insomnia...
, or hypersomnia
Hypersomnia
Hypersomnia is a disorder characterized by excessive amounts of sleepiness.There are two main categories of hypersomnia: primary hypersomnia and recurrent hypersomnia...
. For the sleep-deprived, microsleeping can occur at any time, typically without substantial warning.
Microsleeps (or microsleep episodes) become extremely dangerous when they occur in situations which demand constant alertness, such as driving a motor vehicle
Sleep deprived driving
Sleep-deprived driving is the operation of a motor vehicle while being cognitively impaired by a lack of sleep. Sleep deprivation is a major cause of motor vehicle accidents, and it can impair the human brain as much as alcohol can. According to a 1998 survey, 23% of adults have fallen asleep while...
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.
There is little agreement on how best to identify microsleep episodes. Some experts define microsleep according to behavioral criteria (head nods, drooping eyelids, etc.), while others rely on EEG
EEG
EEG commonly refers to electroencephalography, a measurement of the electrical activity of the brain.EEG may also refer to:* Emperor Entertainment Group, a Hong Kong-based entertainment company...
markers. One study at the University of Iowa
University of Iowa
The University of Iowa is a public state-supported research university located in Iowa City, Iowa, United States. It is the oldest public university in the state. The university is organized into eleven colleges granting undergraduate, graduate, and professional degrees...
defined EEG-monitored microsleeps in driving simulation as "a 3–14 second episode during which 4–7 Hz (theta) activity replaced the waking 8–13 Hz (alpha) background rhythm."
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 accident during a microsleep episode.
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
Waterfall train disaster
The Waterfall rail accident was a train accident that occurred on 31 January 2003 near Waterfall, New South Wales, Australia. The train derailed, killing seven people aboard, including the train driver.-Incident:...
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.