Sleep inertia is a physiological state characterised by a decline in motor dexterity and a subjective feeling of grogginess immediately following an abrupt awakening. The impaired alertness may interfere with the ability to perform mental or physical tasks. Sleep inertia can also refer to the tendency of a person wanting to return to sleep.
NASA studies have shown that a variety of factors influence the severity and duration of sleep inertia. These include:
- Depth of sleep when awakened. After roughly 10–30 minutes, the brain enters into slow-wave sleep. Being awakened during this stage yields more sleep inertia than awakening from other stages of sleep.
- Timing of sleep. Sleep inertia is thought to be related to the phase of the body's circadian rhythm. Waking during a drop in body temperature tends to produce more sleep inertia.
- Chemical influences. Studies have shown that drugs such as caffeine can suppress the effect of sleep inertia, possibly by blocking adenosine receptors in the brain.
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 the deepest sleep have the slowest reaction times.
One theory is that sleep inertia is caused by the build-up of adenosine in the brain during NREM sleep. Adenosine then binds to receptors, and feelings of tiredness result.
See also 
- ^ Tassi, P.; Muzet, A. (2000). "Sleep inertia". Sleep Medicine Reviews 4 (4): 341–353. doi:10.1053/smrv.2000.0098. PMID 12531174.
- ^ Wertz, A.T.; Ronda, J.M.; Czeisler, C.A.; Wright Jr, K.P. (2006). "Effects of Sleep Inertia on Cognition". JAMA: the Journal of the American Medical Association 295 (2): 163–4. doi:10.1001/jama.295.2.163. PMID 16403927.
- ^ "Alertness management: strategic naps in operational settings".
- ^ "Overview, Waking, Non-REM, REM, Sleep Cycle, Factors, Age".
- ^ Sherry, Patrick (June 2000). "Fatigue Countermeasures in the Railroad Industry: Past and Current Developments". University of Denver. Retrieved 2009-05-11.
- ^ Van Dongen, H.P.; Price, N.J.; Mullington, J.M.; Szuba, M.P.; Kapoor, S.C.; Dinges, D.F. (November 2001). "Caffeine eliminates psychomotor vigilance deficits from sleep inertia". Sleep 24 (7): 813–9. PMID 11683484.
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