Editing Sleep inertia

{{Short description|Impaired physiological state after awaking}}
'''Sleep inertia''' is a physiological state of impaired cognitive and sensory-motor performance that is present immediately after awakening. It persists during the transition of [[sleep]] to wakefulness, where an individual will experience feelings of drowsiness, disorientation and a decline in motor [[dexterity]].<ref>{{cite journal|last1=Tassi|first1=P.|last2=Muzet|first2=A.|year=2000|title=Sleep inertia|journal=Sleep Medicine Reviews|volume=4|issue=4|pages=341–353|doi=10.1053/smrv.2000.0098|pmid=12531174}}</ref><ref>{{cite journal|last1=Wertz|first1=A.T.|last2=Ronda|first2=J.M.|last3=Czeisler|first3=C.A.|last4=Wright Jr|first4=K.P.|year=2006|title=Effects of Sleep Inertia on Cognition|journal=JAMA: The Journal of the American Medical Association|volume=295|issue=2|pages=163–4|doi=10.1001/jama.295.2.163|pmid=16403927}}</ref> Impairment from sleep inertia may take several hours to dissipate. In the majority of cases, morning sleep inertia is experienced for 15 to 30 minutes after waking.<ref name=":03">{{cite web|url=http://www.sleepingexpert.org/what-is-sleep-inertia/|title=What Is Sleep Inertia? - Sleeping Expert|website=Sleeping Expert|language=en-US|access-date=2015-11-09|date=2015-10-05}}</ref>

Sleep inertia is of concern with decision-making abilities, safety-critical tasks and the ability to operate efficiently soon after awakening. In these situations, it poses an [[occupational hazard]] due to the cognitive and motor deficits that may be present.

==Symptoms==
* "Grogginess", as defined by a drowsy or disoriented state in which there is a dampening of [[Sensory cue|sensory acuity]] and mental processing.<ref name=":1">{{cite journal|last1=Hilditch|first1=Cassie|last2=McHill|first2=Andrew W|date=2019|title=Sleep inertia: current insights|journal=Nature and Science of Sleep|publisher=Dove Press|volume=11|pages=155–165|doi=10.2147/NSS.S188911|pmid=31692489|pmc=6710480|doi-access=free}}</ref>
* Impaired motor dexterity and decrease in cognitive ability. These gross impairments may be responsible for the associated increase in [[reaction time]] and drop in [[Attention|attentiveness]].<ref name=":1" />
* Deficits in [[spatial memory]]<ref name=":02">{{cite journal|last1=Hilditch|first1=Cassie J.|last2=Dorrian|first2=Jillian|last3=Banks|first3=Siobhan|date=2017-05-02|title=Time to wake up: reactive countermeasures to sleep inertia|journal=Industrial Health|volume=54|issue=6|pages=528–541|doi=10.2486/indhealth.2015-0236|issn=0019-8366|pmc=5136610|pmid=27193071}}</ref>
* Reports of heightened subjective [[fatigue (medical)|fatigue]]
* Reduced [[Vigilance (psychology)|vigilance]] and a desire to go back to sleep<ref>{{Cite journal |last=Trotti |first=Lynn Marie |date=October 2017 |title=Waking up is the hardest thing I do all day: Sleep inertia and sleep drunkenness |journal=Sleep Medicine Reviews |volume=35 |pages=76–84 |doi=10.1016/j.smrv.2016.08.005 |issn=1087-0792 |pmc=5337178 |pmid=27692973}}</ref>
These symptoms are expressed with the greatest intensity immediately after waking, and dissipate following a period of extended wakefulness. The duration of symptoms varies on a conditional basis, with primary expression during the first 15–60 minutes after waking and potentially extending for several hours.<ref name=":02" />  Tasks that require more complex cognitive operations will feature greater deficits as compared to a simple motor task; the [[Accuracy and precision|accuracy]] of sensory and motor functioning is more impaired by sleep inertia as compared to sheer speed.<ref name=":0" />  In order to measure the cognitive and motor deficiencies associated with sleep inertia, a battery of tests may be utilized, including: the [[psychomotor vigilance task]], [[Serial sevens|descending subtraction task]] (DST), [[Reaction time|auditory reaction time task]], and the [[Tapping rate|finger tapping task]].<ref name=":02" /><ref>{{cite web |url=https://www.inverse.com/article/50128-how-long-does-it-take-to-wake-up-the-brain |title=Brain Scans Reveal Why It Takes So Long to Wake Up in the Morning |date=2018-10-24 |access-date=2023-08-01 |website=[[Inverse (website)|Inverse]] |last=Betuel |first=Emma}}</ref>

==Causes==

Studies have shown that abrupt awakening during stage 3 sleep, [[slow-wave sleep]] (SWS), produces more sleep inertia than awakening during sleep stages 1, 2 or [[Rapid eye movement sleep|REM]] sleep.<ref name=":0">{{cite web|url=https://www.researchgate.net/publication/12367344|title=The sleep inertia phenomenon during the sleep-wake transition: Theoretical and operational issues (PDF Download Available)|website=ResearchGate|language=en|access-date=2017-05-02}}</ref> Prior sleep deprivation increases the percentage of time spent in slow-wave sleep (SWS). Therefore, an individual who was previously sleep deprived will have a greater chance of experiencing sleep inertia.<ref name=":1" /><ref name=":0" /> [[Adenosine]] levels in the brain progressively increase with sleep deprivation, and return to normal during sleep.  Upon awakening with sleep deprivation, high amounts of adenosine will be bound to receptors in the brain, neural activity slows down, and a feeling of tiredness will result.<ref>{{cite journal|last1=Newman|first1=Rachel A.|last2=Kamimori|first2=Gary H.|last3=Wesensten|first3=Nancy J.|last4=Picchioni|first4=Dante|last5=Balkin|first5=Thomas J.|title=Caffeine Gum Minimizes Sleep Inertia|journal=Perceptual and Motor Skills|language=en|volume=116|issue=1|pages=280–293|doi=10.2466/29.22.25.pms.116.1.280-293|pmid=23829154|year=2013|s2cid=808008}}</ref> Individuals express a lack of blood flow to the brain upon awakening. Levels of [[Cerebral circulation|cerebral blood flow]] (CBF) and cerebral blood flow velocities (CBFV) will take up to 30 minutes to increase and reach daytime levels.<ref name=":0" />  Cerebral blood flow returns to waking levels in the brainstem and thalamus first. After 15 minutes, the brain's anterior cortical regions receive normal daytime blood flow. This 15 minute time period corresponds to the sleep inertia period.{{cn|date=September 2022}} Additionally, alcoholic beverages in the evening can cause [[Hangover|physiological distress]] upon wake up.<ref>{{cite web|title=Hangovers {{!}} National Institute on Alcohol Abuse and Alcoholism (NIAAA)|url=https://www.niaaa.nih.gov/publications/brochures-and-fact-sheets/hangovers|access-date=2021-11-26|website=www.niaaa.nih.gov}}</ref><ref>{{cite web|title=Hangovers - Symptoms and causes|url=https://www.mayoclinic.org/diseases-conditions/hangovers/symptoms-causes/syc-20373012|access-date=2021-11-26|website=Mayo Clinic|language=en}}</ref>

== Treatments and countermeasures ==
{{Medical citations needed|section|reason=This section relies too much on one source, please consider adding additional reliable third party sources, like medical journal review papers or newspaper articles|date=February 2019}}
There has been a great deal of research into potential methods to relieve the effects of sleep inertia.  The demand for remedies is driven by the [[occupational hazard]]s of sleep inertia for employees who work extended shifts such as medical professionals, emergency responders, or military personnel.  The motor functioning and cognitive ability of these professionals who must immediately respond to a call can pose a safety hazard in the workplace.  Below are some of the various methods that have been suggested to combat sleep inertia.

=== Napping ===
When a person is [[Sleep deprivation|sleep deprived]], re-entering sleep may provide a viable route to reduce mental and physical fatigue, but it can also induce sleep inertia. In order to limit sleep inertia, one should avoid waking from the deeper stages of [[slow-wave sleep]]. The onset of slow-wave sleep occurs approximately 30 minutes after falling asleep, therefore a nap should be limited to under 30 minutes to prevent waking during slow-wave sleep and enhancing sleep inertia. Furthermore, self-awakening from a short nap was shown to relieve disorientation of sleep inertia as opposed to a forced awakening, but these results may warrant more research into the nature of arousal after sleep periods.<ref name=":02"/>

=== Caffeine ===
[[Caffeine]] is a [[xanthine]] derivative that can cross the [[blood–brain barrier]], as well as the most widely-consumed [[stimulant]] compound, present in therapeutic quantities in a variety of food and drink, including [[tea]], [[coffee]], [[soft drink]]s and [[chocolate]]. The caffeine present in coffee or tea exerts its stimulating action by blocking [[adenosine receptor]]s in the brain. By [[Antagonist drug|antagonizing]] the adenosine receptors, caffeine limits the effects of adenosine buildup in the brain and increases alertness and attentiveness. Previous research has shown that coupled with a short nap, consuming caffeine prior to the nap can alleviate the effects of sleep inertia.<ref name=":02"/> Nonetheless, individual degree of consumption and [[Drug tolerance|tolerance]] to caffeine may be responsible for variation in its efficacy to reduce sleep inertia symptoms.

=== Light ===
The natural light provided by the sunrise may contribute to a reduction in sleep inertia effects. Research simulating increase of light at dawn was shown to potentiate the [[cortisol awakening response]] (CAR).<ref name=":02"/> The CAR is a spike in blood cortisol levels following awakening, and is associated with the return to an alert cognitive state.

=== Other ===
Some other interventions that could potentially minimize the effects of sleep inertia are sound and temperature. There is moderate evidence that the presence of mild sounds and a sharp decrease in the temperature of the extremities may independently reverse sleep inertia symptoms.<ref name=":02"/> Sound, especially music, is thought to increase attentiveness and decrease one's subjective feeling of sleepiness upon awakening.<ref name=":02"/> A drop in temperature of the [[Extremities skeleton|extremities]] may prevent heat loss upon awakening, facilitating the return of core body temperature to [[Homeostasis|homeostatic]] daytime levels.<ref name=":02"/>

==See also==
* [[Circadian rhythm sleep disorder]]
* [[Delayed sleep phase syndrome]]
* [[Shift work]]
* [[Confusional arousals]]

==References==
{{reflist}}

==External links==
* [http://national.news21.com/2010-2/pilot-cockpit-napping-ntsb Flying Safely Article on Napping]

{{SleepSeries2}}

{{DEFAULTSORT:Sleep inertia}}
[[Category:Sleep]]
[[Category:Sleep physiology]]
[[Category:Circadian rhythm]]