A power nap or cat nap is a short sleep that terminates before deep sleep (slow-wave sleep; SWS). A power nap is intended to quickly revitalize the sleeper.
A power nap combined with consuming caffeine is called a stimulant nap, coffee nap, caffeine nap, or nappuccino. [1]
A power nap, also known as a Stage 2 nap, is a short slumber of 20 minutes or less which terminates before the occurrence of deep slow-wave sleep, intended to quickly revitalize the napper. The expression "power nap" was coined by Cornell University social psychologist James Maas. [2]
The 20-minute nap increases alertness and motor skills. [2] Various durations may be recommended for power naps, which are short compared to regular sleep. The short duration prevents nappers from sleeping so long that they enter the slow wave portion of the normal sleep cycle without being able to complete the cycle. Entering deep, slow-wave sleep and failing to complete the normal sleep cycle, can result in a phenomenon known as sleep inertia, where one feels groggy, disoriented, and even sleepier than before beginning the nap. In order to attain optimal post-nap performance, a Stage 2 nap must be limited to the beginning of a sleep cycle, specifically sleep stages N1 and N2, typically 18–25 minutes.
Experimental confirmation of the benefits of this brief nap comes from a Flinders University study in Australia in which 5, 10, 20, or 30-minute periods of sleep were given. The greatest immediate improvement in measures of alertness and cognitive performance came after the 10 minutes of sleep. The 20 and 30-minute periods of sleep showed evidence of sleep inertia immediately after the naps and improvements in alertness more than 30 minutes later, but not to a greater level than after the 10 minutes of sleep. [3] Power naps are effective even when schedules allow a full night's sleep. [4]
Power naps intend to restore alertness, performance, and learning ability. [5] [6] A nap may also reverse the hormonal impact of a night of poor sleep or reverse the damage of sleep deprivation. [7] A University of Düsseldorf study found superior memory recall once a person had reached 6 minutes of sleep, suggesting that the onset of sleep may initiate active memory processes of consolidation which—once triggered—remains effective even if sleep is terminated. [6]
According to clinical studies among men and women, power nappers of any frequency or duration had a significantly lower mortality ratio due to heart disease than those not napping. Specifically, those occasionally napping had a 12% lower coronary mortality, whereas those systematically napping had a 37% lower coronary mortality. [8]
A Flinders University study of individuals restricted to only five hours of sleep per night found a 10-minute nap was overall the most recuperative nap duration of various nap lengths they examined (lengths of 0 min, 5 min, 10 min, 20 min, and 30 minutes): the 5-minute nap produced few benefits in comparison with the no-nap control; the 10-minute nap produced immediate improvements in all outcome measures (including sleep onset latency, subjective sleepiness, fatigue, vigor, and cognitive performance), with some of these benefits maintained for as long as 155 minutes; the 20-minute nap was associated with improvements emerging 35 minutes after napping and lasting up to 125 minutes after napping; and the 30-minute nap produced a period of impaired alertness and performance immediately after napping, indicative of sleep inertia, followed by improvements lasting up to 155 minutes after the nap. [9]
The NASA Ames Fatigue Countermeasures Group studied the effects of sleep loss and jet lag, and conducts training to counter these effects. A major fatigue countermeasures recommendation consists of a 40-minute nap ("NASA nap") which empirically showed to improve flight crew performance and alertness with a 22% statistical risk of entering SWS. [10]
For several years, scientists have been investigating the benefits of napping, both the power nap and much longer sleep durations as long as 1–2 hours. Performance across a wide range of cognitive processes has been tested. [10] Studies demonstrate that naps are as good as a night of sleep for some types of memory tasks.
A NASA study led by David F. Dinges, professor at the University of Pennsylvania School of Medicine, found that naps can improve certain memory functions. [11] In that NASA study, volunteers spent several days living on one of 18 different sleep schedules, all in a laboratory setting. To measure the effectiveness of the naps, tests probing memory, alertness, response time, and other cognitive skills were used.
Power Napping Enablers and sleep timers allow properly timed power napping.
One study showed that a midday snooze reverses information overload. Reporting in Nature Neuroscience , Sara Mednick, PhD, Stickgold and colleagues also demonstrated that "burnout" irritation, frustration and poorer performance on a mental task can set in as a day of training wears on. This study also proved that, in some cases, napping could even boost performance to an individual's top levels. The NIMH team wrote: "The bottom line is: we should stop feeling guilty about taking that 'power nap' at work." [12]
The Centers for Disease Control and Prevention studied the effects of socioeconomic status on short sleep durations. In this 2007-2008 CDCP study, 4,850 National Health and Nutrition Examination Survey (NHANES) produced self-reported sleep durations. It was suggested through this study that individuals with minority status and a lower ranking in socioeconomic position are more inclined to have shorter self-reported sleep durations. [13]
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Longer and more frequent daytime naps appeared to be associated with a higher risk of Alzheimer's dementia in a study that tracked 1401 older people over 14 years. [14] [15] Links have also been proposed between these types of naps and cardiovascular disease, though the evidence is largely inconclusive. A series of studies by the medical journal Sleep demonstrated that people who nap for an hour or more a day had 1.82 times the rate of cardiovascular disease than people who didn't nap. [16] [17]
A stimulant nap is a brief period of sleep of around 15 minutes, preceded by consuming a caffeinated drink or another stimulant.
It may combat daytime drowsiness more effectively than napping or drinking coffee alone. [1] [18] [19] A stimulant nap is more effective than regular naps in improving post-nap alertness and cognitive functioning. [20] [21] In a driving simulator and a series of studies, Horne and Reyner investigated the effects of cold air, radio, a break with no nap, a nap, caffeine pill vs. placebo and a short nap preceded by caffeine on mildly sleep-deprived subjects. A nap with caffeine was by far the most effective in reducing driving accidents and subjective sleepiness as it helps the body get rid of the sleep-inducing chemical compound adenosine. [22] [ unreliable source? ] Caffeine in coffee takes up to half an hour to have an alerting effect, hence "a short (<15min) nap will not be compromised if it is taken immediately after the coffee." [23] [24] [25] One account suggested that it was like a "double shot of energy" from the stimulating boost from caffeine plus better alertness from napping. [1] This procedure has been studied on sleep-deprived humans given the task of driving a motor vehicle afterwards, [26] although it has not been studied on elderly populations. [27]
Some companies have nap rooms to allow employees to take power naps. This may be in a form of a nap room with a recliner, or chairs specially designed for power napping installed in a designated area. Companies with nap rooms say that employees are happier and become more productive at work. [29]
Similar nap rooms and stations also exist in higher education institutions. Many colleges and universities provide napping furnitures such as cots and beanbags in libraries for students to take naps after long periods of study. At least one university[ which? ] has a nap room set up in a gym. Some medical schools also set up nap rooms at teaching hospitals. The nap rooms may include sleeping pods or cots, white noise machines, and antimicrobial pillows. [30]
In Barcelona, there is a café called Nappuccino [31] [32] that implements custom-built napping pods inside the café.
A more portable aid is a nap timer app. Apps have various features including aided sounds, nap history and pattern tracking and daily reminders that make it easier to take naps.
Caffeine is a central nervous system (CNS) stimulant of the methylxanthine class and is the most commonly consumed psychoactive substance globally. It is mainly used for its eugeroic, ergogenic, or nootropic (cognitive-enhancing) properties. Caffeine acts by blocking binding of adenosine at a number of adenosine receptor types, inhibiting the centrally depressant effects of adenosine and enhancing the release of acetylcholine. Caffeine has a three-dimensional structure similar to that of adenosine, which allows it to bind and block its receptors. Caffeine also increases cyclic AMP levels through nonselective inhibition of phosphodiesterase, increases calcium release from intracellular stores, and antagonizes GABA receptors, although these mechanisms typically occur at concentrations beyond usual human consumption.
Sleep is a state of reduced mental and physical activity in which consciousness is altered and certain sensory activity is inhibited. During sleep, there is a marked decrease in muscle activity and interactions with the surrounding environment. While sleep differs from wakefulness in terms of the ability to react to stimuli, it still involves active brain patterns, making it more reactive than a coma or disorders of consciousness.
Insomnia, also known as sleeplessness, is a sleep disorder where people have trouble sleeping. They may have difficulty falling asleep, or staying asleep for as long as desired. Insomnia is typically followed by daytime sleepiness, low energy, irritability, and a depressed mood. It may result in an increased risk of accidents of all kinds as well as problems focusing and learning. Insomnia can be short term, lasting for days or weeks, or long term, lasting more than a month. The concept of the word insomnia has two distinct possibilities: insomnia disorder (ID) or insomnia symptoms, and many abstracts of randomized controlled trials and systematic reviews often underreport on which of these two possibilities the word refers to.
Stimulants are a class of drugs that increase alertness. They are used for various purposes, such as enhancing attention, motivation, cognition, mood, and physical performance. Some stimulants are naturally-occuring while others only occur synthetic. Some of the most common stimulants are caffeine, nicotine, amphetamines, cocaine, methylphenidate, and modafinil. Stimulants may be subject to varying forms of regulation, or outright prohibition, depending on jurisdiction.
Polyphasic sleep is the practice of sleeping during multiple periods over the course of 24 hours, in contrast to monophasic sleep, which is one period of sleep within 24 hours. Biphasicsleep refers to two periods, while polyphasic usually means more than two. Segmented sleep and divided sleep may refer to polyphasic or biphasic sleep, but may also refer to interrupted sleep, where the sleep has one or several shorter periods of wakefulness, as was the norm for night sleep in pre-industrial societies.
Hypersomnia is a neurological disorder of excessive time spent sleeping or excessive sleepiness. It can have many possible causes and can cause distress and problems with functioning. In the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), hypersomnolence, of which there are several subtypes, appears under sleep-wake disorders.
A microsleep is a sudden temporary episode of sleep or drowsiness which may last for a few seconds where an individual fails to respond to some arbitrary sensory input and becomes unconscious. Episodes of microsleep occur when an individual loses and regains awareness after a brief lapse in consciousness, often without warning, or when there are sudden shifts between states of wakefulness and sleep. In behavioural terms, microsleeps may manifest as droopy eyes, slow eyelid-closure, and head nodding. In electrical terms, microsleeps are often classified as a shift in electroencephalography (EEG) during which 4–7 Hz activity replaces the waking 8–13 Hz background rhythm.
Shift work is an employment practice designed to keep a service or production line operational at all times. The practice typically sees the day divided into shifts, set periods of time during which different groups of workers perform their duties. The term "shift work" includes both long-term night shifts and work schedules in which employees change or rotate shifts.
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. 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 hygiene is a behavioral and environmental practice developed in the late 1970s as a method to help people with mild to moderate insomnia. Clinicians assess the sleep hygiene of people with insomnia and other conditions, such as depression, and offer recommendations based on the assessment. Sleep hygiene recommendations include establishing a regular sleep schedule, using naps with care, not exercising physically too close to bedtime, limiting worry, limiting exposure to light in the hours before sleep, getting out of bed if sleep does not come, not using bed for anything but sleep and sex, avoiding alcohol in the hours before bedtime, and having a peaceful, comfortable and dark sleep environment.
The Multiple Sleep Latency Test (MSLT) is a sleep disorder diagnostic tool. It is used to measure the time elapsed from the start of a daytime nap period to the first signs of sleep, called sleep latency. The test is based on the idea that the sleepier people are, the faster they will fall asleep.
Shift work sleep disorder (SWSD) is a circadian rhythm sleep disorder characterized by insomnia, excessive sleepiness, or both affecting people whose work hours overlap with the typical sleep period. Insomnia can be the difficulty to fall asleep or to wake up before the individual has slept enough. About 20% of the working population participates in shift work. SWSD commonly goes undiagnosed, and it is estimated that 10–40% of shift workers have SWSD. The excessive sleepiness appears when the individual has to be productive, awake and alert. Both symptoms are predominant in SWSD. There are numerous shift work schedules, and they may be permanent, intermittent, or rotating; consequently, the manifestations of SWSD are quite variable. Most people with different schedules than the ordinary one might have these symptoms but the difference is that SWSD is continual, long-term, and starts to interfere with the individual's life.
Alertness is a state of active attention characterized by high sensory awareness. Someone who is alert is vigilant and promptly meets danger or emergency, or is quick to perceive and act. Alertness is a psychological and physiological state.
Caffeine-induced sleep disorder was a psychiatric disorder identified as resulting from overconsumption of the stimulant caffeine.
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 widely in severity. All known animals sleep or exhibit some form of sleep behavior, and the importance of sleep is self-evident for humans, as nearly a third of a person's life is spent sleeping. Sleep deprivation is common as it affects about one-third of the population.
Narcolepsy is a chronic neurological disorder that impairs the ability to regulate sleep–wake cycles, and specifically impacts REM sleep. The pentad symptoms of narcolepsy include excessive daytime sleepiness (EDS), sleep-related hallucinations, sleep paralysis, disturbed nocturnal sleep (DNS), and cataplexy. People with narcolepsy tend to sleep about the same number of hours per day as people without it, but the quality of sleep is typically compromised.
A nap is a short period of sleep, typically taken during daytime hours as an adjunct to the usual nocturnal sleep period. Naps are most often taken as a response to drowsiness during waking hours. A nap is a form of biphasic or polyphasic sleep, where the latter terms also include longer periods of sleep in addition to one period. For years, scientists have been investigating the benefits of napping, including the 30-minute nap as well as sleep durations of 1–2 hours. Performance across a wide range of cognitive processes has been tested.
Idiopathic hypersomnia(IH) is a neurological disorder which is characterized primarily by excessive sleep and excessive daytime sleepiness (EDS). Idiopathic hypersomnia was first described by Bedrich Roth in 1976, and it can be divided into two forms: polysymptomatic and monosymptomatic. The condition typically becomes evident in early adulthood and most patients diagnosed with IH will have had the disorder for many years prior to their diagnosis. As of August 2021, an FDA-approved medication exists for IH called Xywav, which is an oral solution of calcium, magnesium, potassium, and sodium oxybates; in addition to several off-label treatments (primarily FDA-approved narcolepsy medications).
Sleep deprivation – the condition of not having enough sleep – is a common health issue for students in higher education. This issue has several underlying and negative consequences, but there are a few helpful improvements that students can make to reduce its frequency and severity.
Caffeine use for sport is a worldwide known and tested idea. Many athletes use caffeine as a legal performance enhancer, as the benefits it provides, both physically and cognitively outweigh the disadvantages. The benefits caffeine provides influences the performance of both endurance athletes and anaerobic athletes. Caffeine has been proven to be effective in enhancing performance.