groggy adj : stunned or confused and slow to react (as from blows or drunkenness or exhaustion) [syn: dazed, foggy, logy, stuporous] [also: groggiest, groggier]
- Rhymes: -ɒɡi
Sleep inertia is a physiological state characterised by a decline in motor dexterity and a subjective feeling of grogginess, immediately following an abrupt awakening. Sleep inertia can also refer to the tendency of a person to want to return to sleeping, even after suitable rest has been achieved. Typically, sleep inertia lasts up to 3 hours for a night wake up and up to 90 minutes for a day wake up. If the subject is awakened due to a perceived danger, however, the duration of sleep inertia is reduced to only a few seconds.
FactorsNASA studies have shown that a variety of factors influence the severity and duration of sleep inertia. These include:
- Depth of sleep when woken. After roughly 30 minutes, the body enters into deep sleep. More sleep inertia than otherwise occurs when awakening from deep sleep, that is, stages 3 and 4 of NREM.
- Time of sleep. Sleep inertia is thought to be related to the phase of the body's circadian rhythm. Waking during a trough in body temperature tends to produce more sleep inertia.
- Chemical influences. Studies have shown that drugs such as caffeine suppress the effect of sleep inertia, possibly by blocking adenosine receptors in the brain.
According to Patrick Sherry, who specializes in rail safety, sleep inertia can be more severe and last longer when a nap follows a prolonged period of wakefulness or an accumulated sleep debt. Sleep inertia can often be reversed by activity and noise as well as caffeine. Reaction time performance is directly related to sleep stage at awakening; persons awakened during stage 4 sleep (the deepest) yield maximum reaction times.
CauseOne theory is that sleep inertia is caused by the build-up of adenosine in the brain during non-REM sleep. Adenosine then binds to receptors, which produce the feelings of tiredness.
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