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Nap

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For other uses, see Nap (disambiguation).

A man napping in a hammock, on a patio in Costa Rica

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.[1]

Benefits

Sara Mednick conducted a study experimenting on the effects of napping, caffeine, and a placebo. Her results showed that a 60–90-minute nap is more effective than caffeine in memory and cognition.[2]

Power nap

Main article: Power nap

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 power nap is meant to maximize the benefits of sleep versus time. It is used to supplement normal sleep, especially when a sleeper has accumulated a sleep deficit. The greater the sleep deficit, the more effective the nap.[3]

Prescribed napping for sleep disorders

It has been shown that excessive daytime sleepiness (EDS) can be improved by prescribed napping in narcolepsy.[4] Apart from narcolepsy, it has not been demonstrated that naps are beneficial for EDS in other sleep disorders.[4]

Learning and memory

Research suggests that shorter, habitual naps after instruction offer the most benefits to learning.[5][6] The benefits to alertness show no change based on duration of the nap for combating post-lunch dip, even for naps as short as 10 minutes.[7] Napping enhances alertness in young adults and adolescents during afternoons’ performances, which affect efficiency.[8] Additionally, pre-teens who nap regularly during the day demonstrate better sleep at night. In younger children, napping increased drowsiness even while improving memory recall.[9]

For students of all ages, napping during the school day showed benefits to reaction time and recall of declarative memory of new information, especially if the naps remain in slow-wave sleep, i.e. less than an hour in length.[10][6]

Cognitive capacity

In adults, a causal association has been found between habitual daytime napping and larger brain volume.[11] Brain volume normally declines with age, and is associated with neurodegenerative disease.[11] Earlier studies have shown benefits of napping for cognitive performance for healthy adults.[11]

Alertness and fatigue

The circadian cycle plays a role in the rising demand for daytime naps: sleepiness rises towards the mid-afternoon, hence the best timing for naps is early afternoon.[12][citation not found] Twenty- to thirty-minute naps are recommended for adults, while young children and elderly people may need longer naps.[13][14] Research, on the other hand, has shown that the benefits of napping depend on sleep onset and sleep phases rather than time and duration.[15]

Negative effects

Sleep inertia

The state of grogginess, impaired cognition and disorientation experienced when awakening from sleep is known as sleep inertia.[16] This state reduces the speed of cognitive tasks but has no effects on the accuracy of task performance.[4] The effects of sleep inertia rarely last longer than 30 minutes in the absence of prior sleep deprivation.[17]

Potential health risks

A 2016 meta-analysis showed that there may be a correlation with habitual napping for more than an hour, and an increased risk for cardiovascular disease, diabetes, metabolic syndrome or death.[18] There was no effect of napping for as long as 40  minutes per day, but a sharp increase in risk of disease occurred at longer nap times. No causal relationship was established: the link may be to do with people taking a longer nap in response to the pre-existence of other risk factors.[18]

Habitual naps are also an indicator of neurological degradation such as dementia in the elderly, as reduction in brain function causes more sleepiness.[19]

On sleep disorders

For idiopathic hypersomnia, patients typically experience sleep inertia and are unrefreshed after napping.[20]

Best practices

How long and when a person naps affects sleep inertia and sleep latency: a person is more likely to benefit in terms of those two points when they sleep moderately in the afternoon. According to research, the degree to which a person experiences sleep inertia differs in different durations of nap. Because sleep inertia is possibly resulting from awakening from slow-wave sleep, it is more likely to happen when one has a longer nap.[21] Sleep inertia is less intense after short naps.[22] Sleep latency is shorter when a nap is taken between 3 and 5 pm, compared with a nap taken between 7 and 9 pm.[23]

According to The Sleep Foundation, Psychology Today and Harvard Health Publishing, these are the best practices for napping:[13][24][14]

  • Setting up a sleep-friendly environment.
  • Understanding physical needs
  • Setting an alarm in order to prevent the negative impact of sleep inertia and sleep latency

See also

References

  1. ^ Rosekind MR, Smith RM, Miller DL, Co EL, Gregory, Webbon LL, et al. (December 1995). "Alertness management: strategic naps in operational settings". Journal of Sleep Research. 4 (S2): 62–66. doi:10.1111/j.1365-2869.1995.tb00229.x. PMID 10607214. S2CID 23583942.
  2. ^ Mednick SC, Cai DJ, Kanady J, Drummond SP (November 2008). "Comparing the benefits of caffeine, naps and placebo on verbal, motor and perceptual memory". Behavioural Brain Research. 193 (1): 79–86. doi:10.1016/j.bbr.2008.04.028. PMC 2603066. PMID 18554731.
  3. ^ "Temporal Placement of a Nap for Alertness: Contributions of Circadian Phase and Prior Wakefulness". Sleep. 1 July 1987. doi:10.1093/sleep/10.4.313. ISSN 1550-9109.
  4. ^ a b c Takahashi M (June 2003). "The role of prescribed napping in sleep medicine". Sleep Medicine Reviews. 7 (3): 227–35. doi:10.1053/smrv.2002.0241. PMID 12927122.
  5. ^ Lemos N, Weissheimer J, Ribeiro S (3 June 2014). "Naps in school can enhance the duration of declarative memories learned by adolescents". Frontiers in Systems Neuroscience. 8: 103. doi:10.3389/fnsys.2014.00103. PMC 4042263. PMID 24917794.
  6. ^ a b Ji X, Li J, Liu J (February 2018). "The Relationship Between Midday Napping And Neurocognitive Function in Early Adolescents". Behavioral Sleep Medicine. 17 (5): 537–551. doi:10.1080/15402002.2018.1425868. PMC 6669094. PMID 29388804.
  7. ^ Takahashi M, Nakata A, Haratani T, Ogawa Y, Arito H (July 2004). "Post-lunch nap as a worksite intervention to promote alertness on the job". Ergonomics. 47 (9): 1003–1013. doi:10.1080/00140130410001686320. PMID 15204275. S2CID 37556310.
  8. ^ Takahashi M, Fukuda H, Arito H (July 1998). "Brief naps during post-lunch rest: effects on alertness, performance, and autonomic balance". European Journal of Applied Physiology and Occupational Physiology. 78 (2): 93–98. doi:10.1007/s004210050392. PMID 9694306. S2CID 2601267.
  9. ^ Tietzel AJ, Lack LC (September 2002). "The recuperative value of brief and ultra-brief naps on alertness and cognitive performance". Journal of Sleep Research. 11 (3): 213–218. doi:10.1046/j.1365-2869.2002.00299.x. PMID 12220317. S2CID 22706866.
  10. ^ Tucker MA, Hirota Y, Wamsley EJ, Lau H, Chaklader A, Fishbein W (September 2006). "A daytime nap containing solely non-REM sleep enhances declarative but not procedural memory". Neurobiology of Learning and Memory. 86 (2): 241–247. doi:10.1016/j.nlm.2006.03.005. PMID 16647282. S2CID 17606945.
  11. ^ a b c Paz V, Dashti HS, Garfield V (2023). "Is there an association between daytime napping, cognitive function, and brain volume? A Mendelian randomization study in the UK Biobank". Sleep Health. 9 (5): 786–793. doi:10.1016/j.sleh.2023.05.002. PMID 37344293.
  12. ^ Stampi 1992; Bertisch as cited in Bilodeau 2021.
  13. ^ a b "Napping May Not Be Such a No-No". Harvard Health. 1 November 2009. Retrieved 18 February 2023.
  14. ^ a b Chan OY, Phoon WH, Gan SL, Ngui SJ (October 1989). "Sleep-wake patterns and subjective sleep quality of day and night workers: interaction between napping and main sleep episodes". Sleep. 12 (5): 439–448. doi:10.1093/sleep/12.5.439. PMID 2799217.
  15. ^ Jones BJ, Spencer RM (December 2020). "Role of Napping for Learning across the Lifespan". Current Sleep Medicine Reports. 6 (4): 290–297. doi:10.1007/s40675-020-00193-9. PMC 8011550. PMID 33816064.
  16. ^ Dinges DF (1990). "Are you awake? Cognitive performance and reverie during the hypnopompic state.". In Bootzin R, Kihlstrom J, Schacter D (eds.). Sleep and Cognition. Washington, DC: American Psychological Society. pp. 159–175. doi:10.1037/10499-012. ISBN 1-55798-083-7.
  17. ^ Tassi P, Muzet A (August 2000). "Sleep inertia". Sleep Medicine Reviews. 4 (4): 341–353. doi:10.1053/smrv.2000.0098. PMID 12531174.
  18. ^ a b Yamada T, Shojima N, Yamauchi T, Kadowaki T (December 2016). "J-curve relation between daytime nap duration and type 2 diabetes or metabolic syndrome: A dose-response meta-analysis". Scientific Reports. 6 (1): 38075. doi:10.1038/srep38075. PMC 5133463. PMID 27909305.
  19. ^ Mantua J, Spencer RM (September 2017). "Exploring the nap paradox: are mid-day sleep bouts a friend or foe?". Sleep Medicine. 37: 88–97. doi:10.1016/j.sleep.2017.01.019. PMC 5598771. PMID 28899546.
  20. ^ Choo KL, Guilleminault C (March 1998). "Narcolepsy and idiopathic hypersomnolence". Clinics in Chest Medicine. 19 (1): 169–81. doi:10.1016/s0272-5231(05)70440-8. PMID 9554226.
  21. ^ Milner CE, Cote KA (June 2009). "Benefits of napping in healthy adults: impact of nap length, time of day, age, and experience with napping". Journal of Sleep Research. 18 (2): 272–281. doi:10.1111/j.1365-2869.2008.00718.x. PMID 19645971. S2CID 22815227.
  22. ^ Santos JS, Beijamini F, Louzada FM (28 July 2021). "Napping Behavior in Adolescents: Consensus, Dissents, and Recommendations". Sleep and Vigilance. 5 (2): 189–196. doi:10.1007/s41782-021-00155-3. ISSN 2510-2265. S2CID 237714078.
  23. ^ Shrivastava D, Jung S, Saadat M, Sirohi R, Crewson K (January 2014). "How to interpret the results of a sleep study". Journal of Community Hospital Internal Medicine Perspectives. 4 (5): 24983. doi:10.3402/jchimp.v4.24983. PMC 4246141. PMID 25432643.
  24. ^ Andrews LW (5 June 2010). "Ultimate Napping: A How-To Guide". Psychology Today. Retrieved 18 February 2023.
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