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 Sleep is a sedentary state of mind and body. It is characterized by altered consciousness, relatively inhibited sensory activity, reduced muscle activity and reduced interactions with surroundings. It is distinguished from wakefulness by a de ...

to wakefulness, where an individual will experience feelings of drowsiness, disorientation and a decline in motor

dexterity Fine motor skill (or dexterity) is the coordination of small muscles in movement with the eyes, hands and fingers. The complex levels of manual dexterity that humans exhibit can be related to the nervous system. Fine motor skills aid in the growt ...

. 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. 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 An occupational hazard is a hazard experienced in the workplace. This encompasses many types of hazards, including chemical hazards, biological hazards (biohazards), psychosocial hazards, and physical hazards. In the United States, the Nation ...

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 acuity and mental processing. * Impaired motor dexterity and decrease in cognitive ability. These gross impairments may be responsible for the associated increase in

reaction time Mental chronometry is the scientific study of processing speed or reaction time on cognitive tasks to infer the content, duration, and temporal sequencing of mental operations. Reaction time (RT; sometimes referred to as "response time") is meas ...

and drop in attentiveness. * Deficits in

spatial memory In cognitive psychology and neuroscience, spatial memory is a form of memory responsible for the recording and recovery of information needed to plan a course to a location and to recall the location of an object or the occurrence of an event. Sp ...

* Reports of heightened subjective

fatigue Fatigue describes a state of tiredness that does not resolve with rest or sleep. In general usage, fatigue is synonymous with extreme tiredness or exhaustion that normally follows prolonged physical or mental activity. When it does not resolve ...

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. Tasks that require more complex cognitive operations will feature greater deficits as compared to a simple motor task; the

accuracy Accuracy and precision are two measures of ''observational error''. ''Accuracy'' is how close a given set of measurements (observations or readings) are to their ''true value'', while ''precision'' is how close the measurements are to each other ...

of sensory and motor functioning is more impaired by sleep inertia as compared to sheer speed. In order to measure the cognitive and motor deficiencies associated with sleep inertia, a battery of tests may be utilized including

psychomotor vigilance task A psychomotor vigilance task (PVT) is a sustained-attention, reaction-timed task that measures the consistency with which subjects respond to a visual stimulus. Research indicates increased sleep debt or sleep deficit correlates with deteriorated ...

, descending subtraction task (DST), auditory reaction time task, and the finger tapping task.

Causes

* Studies have shown that abrupt awakening during stage 3 sleep,

slow-wave sleep Slow-wave sleep (SWS), often referred to as deep sleep, consists of stage three of non-rapid eye movement sleep. It usually lasts between 70 and 90 minutes and takes place during the first hours of the night. Initially, SWS consisted of both St ...

(SWS), produces more sleep inertia than awakening during sleep stages 1, 2 or

REM Rem or REM may refer to: Music * R.E.M., an American rock band * ''R.E.M.'' (EP), by Green * "R.E.M." (song), by Ariana Grande Organizations * La République En Marche!, a French centrist political party * Reichserziehungsministerium, in Nazi G ...

sleep. * 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. *

Adenosine Adenosine ( symbol A) is an organic compound that occurs widely in nature in the form of diverse derivatives. The molecule consists of an adenine attached to a ribose via a β-N9-glycosidic bond. Adenosine is one of the four nucleoside building ...

levels in the brain progressively increase with sleep deprivation, and return to normal during sleep. Upon awakening with sleep deprivation, high amounts of

adenosine Adenosine ( symbol A) is an organic compound that occurs widely in nature in the form of diverse derivatives. The molecule consists of an adenine attached to a ribose via a β-N9-glycosidic bond. Adenosine is one of the four nucleoside building ...

will be bound to receptors in the brain, neural activity slows down, and a feeling of tiredness will result. * Studies show that individuals express a lack of blood flow to the brain upon awakening. Levels of

cerebral blood flow Cerebral circulation is the movement of blood through a network of cerebral arteries and veins supplying the brain. The rate of cerebral blood flow in an adult human is typically 750 milliliters per minute, or about 15% of cardiac output. Arterie ...

(CBF) and cerebral blood flow velocities (CBFV) will take up to 30 minutes to increase and reach daytime levels. Studies using advanced imaging have shown that cerebral blood flow will return to waking levels in the brainstem and thalamus first. Then, 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. *Studies show that drinking alcoholic beverages in the evening causes physiological distress upon wake up. This phenomenon is known colloquially as a

hangover A hangover is the experience of various unpleasant physiological and psychological effects usually following the consumption of alcohol, such as wine, beer, and liquor. Hangovers can last for several hours or for more than 24 hours. Typical sympto ...

Treatments / countermeasures

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

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

professional A professional is a member of a profession or any person who works in a specified professional activity. The term also describes the standards of education and training that prepare members of the profession with the particular knowledge and skil ...

s 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 deprived Sleep deprivation, also known as sleep insufficiency or sleeplessness, is the condition of not having adequate duration and/or quality of sleep to support decent alertness, performance, and health. It can be either chronic or acute and may vary ...

, 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

. 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.

Caffeine

Caffeine Caffeine is a central nervous system (CNS) stimulant of the methylxanthine class. It is mainly used recreationally as a cognitive enhancer, increasing alertness and attentional performance. Caffeine acts by blocking binding of adenosine t ...

is a

xanthine Xanthine ( or ; archaically xanthic acid; systematic name 3,7-dihydropurine-2,6-dione) is a purine base (genetics), base found in most human body tissues and fluids, as well as in other organisms. Several stimulants are derived from xanthine, incl ...

derivative that can cross the blood-brain barrier. The caffeine present in coffee or tea exerts its stimulating action by blocking

adenosine receptor The adenosine receptors (or P1 receptors) are a class of purinergic G protein-coupled receptors with adenosine as the endogenous ligand. There are four known types of adenosine receptors in humans: A1, A2A, A2B and A3; each is encoded by a di ...

s in the brain. By 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. Nonetheless, individual degree of consumption and

tolerance Tolerance or toleration is the state of tolerating, or putting up with, conditionally. Economics, business, and politics * Toleration Party, a historic political party active in Connecticut * Tolerant Systems, the former name of Veritas Software ...

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 The cortisol awakening response (CAR) is an increase between 38% and 75% in cortisol levels peaking 30–45 minutes ''after'' awakening in the morning in some people. This rise is superimposed upon the late-night rise in cortisol which occurs ...

(CAR). 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. Noise, especially music, is thought to increase attentiveness and decrease one's subjective feeling of sleepiness upon awakening. A drop in temperature of the extremities may prevent heat loss upon awakening, facilitating the return of core body temperature to homeostatic daytime levels.

References

External links

Flying Safely Article on Napping
{{DEFAULTSORT:Sleep Inertia Sleep Sleep physiology Circadian rhythm