Biology:Nap

From HandWiki

A nap is a short period of sleep,[1] 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 or as a means to supplement before or after loss of sleep. 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. There are multiple different types of naps depending on what the user's desired outcome may be or time constraints they may have, and 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, and naps have been shown to have various cognitive, physical, and psychosocial benefits.[2][1]

Types of naps

Agricultural workers napping on the flax they harvested

Naps can be categorized based on their purpose and duration [3]

Purpose classifications

  • Power nap: A short nap designed to rejuvenate the individual quickly without entering deep sleep stages, thereby minimizing sleep inertia.
  • Recovery nap: Taken to compensate for sleep loss that has already occurred, these naps help alleviate fatigue resulting from insufficient nocturnal sleep.
  • Prophylactic nap: Planned in anticipation of sleep deprivation, such as before extended work hours or night shifts, to maintain alertness and performance.
  • Safety nap: Scheduled by professionals such as firefighters, pilots, truck drivers, and healthcare workers to reduce the risk of errors or accidents, and often institutionally or legally mandated as part of one's workload.[4][5]
  • Appetitive nap: Napping for enjoyment or relaxation, even when not sleep-deprived.
  • Habitual nap: Naps taken as part of a daily routine rather than as a response to fatigue or deprivation. Common in cultures that practice siestas, or among age groups like young children and older adults.[6]
  • Caffeine nap:  A nap taken soon after consuming caffeine or coffee to take advantage of the delayed caffeine absorption to even more enhance focus and alertness upon waking.[7]
  • Essential Nap: During times of illness or when in need of recovery, essential naps are taken to support healing and boost the immune system.[8][9]

Duration classifications

Napping practices can be categorized based on duration, each offering distinct benefits and considerations:

  1. Micro nap (2–5 minutes): Extremely short naps lasting 2 to 5 minutes can enhance alertness and reduce fatigue while staying in the light sleep stages. Micro naps should not be confused with microsleeps, which are short lapses in wakefulness that occur while a person is attempting to stay awake and can be dangerous for the individual and people around them if not addressed quickly.[10]
  2. Power nap (10–30 minutes): Power naps typically last between 10 and 30 minutes and are designed to improve alertness and performance without the grogginess associated with deeper sleep stages.[11] The power nap is meant to maximize the benefits of sleep relative to time. It supplements normal sleep, especially when a sleeper has accumulated a sleep deficit. The greater the sleep deficit, the more effective the nap.[12]
  3. NASA nap (26 minutes): Based on research by NASA, a 26-minute nap has been shown to enhance alertness by 54% and performance by 34% among pilots and astronauts.[13]
  4. Slow-wave sleep nap (30–60 minutes): Naps lasting 30 to 60 minutes allow the body to enter slow-wave sleep, which is beneficial for decision-making skills and memorization.[14] However, waking up during this phase may result in increased sleep inertia.
  5. Full sleep cycle nap (90 minutes): A 90-minute nap typically encompasses a full sleep cycle, including light sleep, deep sleep, and REM sleep. This duration can enhance procedural memory and creativity and usually avoids sleep inertia, as the napper completes the full cycle.[15]

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.[16]

Benefits to napping

Learning and memory

Research suggests that shorter, habitual naps after instruction offer the most benefits to learning.[17][18] 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.[19] Napping enhances alertness in young adults and adolescents during afternoons' performances, which affect efficiency.[20] 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.[21]

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.[22][18]

Cognitive capacity

In adults, a causal association has been found between habitual daytime napping and larger brain volume.[23] Brain volume normally declines with age, and is associated with neurodegenerative disease.[23] Earlier studies have shown benefits of napping for cognitive performance for healthy adults.[23]

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.[24] Twenty- to thirty-minute naps are recommended for adults, while young children and elderly people may need longer naps.[25][26] Research, on the other hand, has shown that the benefits of napping depend on sleep onset and sleep phases rather than time and duration.[27]

Prescribed napping

It has been shown that excessive daytime sleepiness (EDS) can be improved by prescribed napping in narcolepsy.[28] Apart from narcolepsy, it has not been demonstrated that naps are beneficial for EDS in other sleep disorders.[28] For idiopathic hypersomnia, patients typically experience sleep inertia and are unrefreshed after napping.[29]

For healthy individuals in need of cognitive or emotional improvement, prescribed naps may be beneficial.[30] However, excessive napping, especially in adults with other health conditions, may be linked with negative outcomes and should be approached holistically and with caution.[30]

Negative effects of napping

Sleep inertia

The state of grogginess, impaired cognition and disorientation experienced when awakening from sleep is known as sleep inertia.[31] This state reduces the speed of cognitive tasks but has no effects on the accuracy of task performance.[28] The effects of sleep inertia rarely last longer than 30 minutes in the absence of prior sleep deprivation.[32]

Potential health risks

A 2016 meta-analysis showed that there may be a correlation between habitual napping for more than an hour, and having an increased risk for cardiovascular disease, diabetes, metabolic syndrome or death.[33] 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.[33]

Habitual naps are also an indicator of neurological degradation such as dementia in the elderly, as reduction in brain function causes more sleepiness.[34]

Naps across the lifespan

The need and benefits of napping vary across different age groups since sleep patterns and requirements across a person's lifespan vary with time.[35]

  • Infants and young children: Regular naps are crucial for growth, development, and mood regulation. They contribute significantly to memory consolidation and learning processes.
  • Adolescents: Napping can improve mood, alertness, and academic performance, especially when nighttime sleep is insufficient. Some research suggests that the biological changes marked by puberty in adolescents are highly correlated to a later sleep onset time, lower sleep efficiency, and other sleep pattern changes that might point to why adolescents, especially older adolescents, may require more naps.[36][37]
  • Adults: Short naps can enhance cognitive functions, mood, and alertness. However, longer naps may lead to sleep inertia and could be associated with health risks if they disrupt nighttime sleep. Adults requiring frequent daytime naps might have underlying sleep conditions, such as sleep apnea, that might need medical attention.
  • Older adults: As sleep efficiency decreases with age,[38] sleep patterns in older adults may shift towards napping more frequently to maintain performance without detriment to nocturnal sleep. Evidence shows that older adults with chronic health conditions may take naps to offset fatigue from their comorbidities rather than fatigue based solely on their age.[39][40]

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.[41] Sleep inertia is less intense after short naps.[42] Sleep latency is shorter when a nap is taken between 3 and 5 pm, compared with a nap taken between 7 and 9 pm.[43]

According to The Sleep Foundation, Psychology Today and Harvard Health Publishing, these are the best practices for napping:[25][44][26]

  • Setting up a sleep-friendly environment
    • Dark room
    • Quiet atmosphere
    • Only using the bed for sleep
    • Limiting electronic use prior to sleep
  • Understanding physical needs
  • Setting an alarm in order to prevent the negative impact of sleep inertia and sleep latency

See also

References

  1. ↑ 1.0 1.1 Lovato, Nicole; Lack, Leon (2010). "The effects of napping on cognitive functioning". Progress in Brain Research. 185. Elsevier. pp. 155–166. doi:10.1016/b978-0-444-53702-7.00009-9. ISBN 978-0-444-53702-7. https://linkinghub.elsevier.com/retrieve/pii/B9780444537027000099. Retrieved 2025-04-08. "Naps (brief sleeps) are a global and highly prevalent phenomenon" 
  2. ↑ "Alertness management: strategic naps in operational settings". Journal of Sleep Research 4 (S2): 62–66. December 1995. doi:10.1111/j.1365-2869.1995.tb00229.x. PMID 10607214. 
  3. ↑ "What Are the Different Types of Naps?" (in en-US). Sleep Doctor. 2022-12-13. https://sleepdoctor.com/napping/types-of-naps. 
  4. ↑ Caldwell, John A.; Mallis, Melissa M.; Caldwell, J. Lynn; Paul, Michel A.; Miller, James C.; Neri, David F.; Aerospace Medical Association Fatigue Countermeasures Subcommittee of the Aerospace Human Factors Committee (January 2009). "Fatigue countermeasures in aviation". Aviation, Space, and Environmental Medicine 80 (1): 29–59. doi:10.3357/asem.2435.2009. ISSN 0095-6562. PMID 19180856. 
  5. ↑ Sieberichs, Sebastian; Kluge, Annette (September 2018). "Effects of In-Flight Countermeasures to Mitigate Fatigue Risks in Aviation". Aviation Psychology and Applied Human Factors 8 (2): 86–92. doi:10.1027/2192-0923/a000143. ISSN 2192-0923. https://econtent.hogrefe.com/doi/10.1027/2192-0923/a000143. 
  6. ↑ Vizmanos, Barbara; Cascales, Ana Isabel; Rodríguez-Martín, María; Salmerón, Diego; Morales, Eva; Aragón-Alonso, Aurora; Scheer, Frank A. J. L.; Garaulet, Marta (2023). "Lifestyle mediators of associations among siestas, obesity, and metabolic health" (in en). Obesity 31 (5): 1227–1239. doi:10.1002/oby.23765. ISSN 1930-739X. PMID 37140401. 
  7. ↑ Reyner, L. A.; Horne, J. A. (November 1997). "Suppression of sleepiness in drivers: combination of caffeine with a short nap". Psychophysiology 34 (6): 721–725. doi:10.1111/j.1469-8986.1997.tb02148.x. ISSN 0048-5772. PMID 9401427. 
  8. ↑ Lange, Tanja; Dimitrov, Stoyan; Born, Jan (April 2010). "Effects of sleep and circadian rhythm on the human immune system". Annals of the New York Academy of Sciences 1193 (1): 48–59. doi:10.1111/j.1749-6632.2009.05300.x. ISSN 1749-6632. PMID 20398008. Bibcode: 2010NYASA1193...48L. 
  9. ↑ Besedovsky, Luciana; Lange, Tanja; Born, Jan (January 2012). "Sleep and immune function". Pflügers Archiv: European Journal of Physiology 463 (1): 121–137. doi:10.1007/s00424-011-1044-0. ISSN 1432-2013. PMID 22071480. 
  10. ↑ thensf (2021-10-30). "What is Microsleep?" (in en-US). https://www.thensf.org/what-is-microsleep/. 
  11. ↑ Lastella, Michele; Halson, Shona L.; Vitale, Jacopo A.; Memon, Aamir R.; Vincent, Grace E. (2021-06-24). "To Nap or Not to Nap? A Systematic Review Evaluating Napping Behavior in Athletes and the Impact on Various Measures of Athletic Performance" (in English). Nature and Science of Sleep 13: 841–862. doi:10.2147/NSS.S315556. PMID 34194254. 
  12. ↑ "Temporal Placement of a Nap for Alertness: Contributions of Circadian Phase and Prior Wakefulness". Sleep. 1987-07-01. doi:10.1093/sleep/10.4.313. ISSN 1550-9109. 
  13. ↑ Rosekind, Mark R.; Graeber, R. Curtis; Dinges, David F.; Connell, Linda J.; Rountree, Michael S.; Spinweber, Cheryl L.; Gillen, Kelly A. (1994-09-01) (in en). Crew factors in flight operations 9: Effects of planned cockpit rest on crew performance and alertness in long-haul operations. https://ntrs.nasa.gov/citations/19950006379. 
  14. ↑ Stepan, Michelle E.; Altmann, Erik M.; Fenn, Kimberly M. (2021-11-12). "Slow-wave sleep during a brief nap is related to reduced cognitive deficits during sleep deprivation". Sleep 44 (11). doi:10.1093/sleep/zsab152. ISSN 1550-9109. PMID 34156468. 
  15. ↑ Patel, Aakash K.; Reddy, Vamsi; Shumway, Karlie R.; Araujo, John F. (2025), "Physiology, Sleep Stages", StatPearls (Treasure Island (FL): StatPearls Publishing), PMID 30252388, https://www.ncbi.nlm.nih.gov/books/NBK526132/, retrieved 2025-03-17 
  16. ↑ "Comparing the benefits of caffeine, naps and placebo on verbal, motor and perceptual memory". Behavioural Brain Research 193 (1): 79–86. November 2008. doi:10.1016/j.bbr.2008.04.028. PMID 18554731. 
  17. ↑ "Naps in school can enhance the duration of declarative memories learned by adolescents". Frontiers in Systems Neuroscience 8: 103. 2014-06-03. doi:10.3389/fnsys.2014.00103. PMID 24917794. 
  18. ↑ 18.0 18.1 "The Relationship Between Midday Napping And Neurocognitive Function in Early Adolescents". Behavioral Sleep Medicine 17 (5): 537–551. February 2018. doi:10.1080/15402002.2018.1425868. PMID 29388804. 
  19. ↑ "Post-lunch nap as a worksite intervention to promote alertness on the job". Ergonomics 47 (9): 1003–1013. July 2004. doi:10.1080/00140130410001686320. PMID 15204275. 
  20. ↑ "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. July 1998. doi:10.1007/s004210050392. PMID 9694306. 
  21. ↑ "The recuperative value of brief and ultra-brief naps on alertness and cognitive performance". Journal of Sleep Research 11 (3): 213–218. September 2002. doi:10.1046/j.1365-2869.2002.00299.x. PMID 12220317. 
  22. ↑ "A daytime nap containing solely non-REM sleep enhances declarative but not procedural memory". Neurobiology of Learning and Memory 86 (2): 241–247. September 2006. doi:10.1016/j.nlm.2006.03.005. PMID 16647282. 
  23. ↑ 23.0 23.1 23.2 "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. 2023. doi:10.1016/j.sleh.2023.05.002. PMID 37344293. 
  24. ↑ Leong, Ruth L F; Lau, TeYang; Dicom, Andrew R; Teo, Teck Boon; Ong, Ju Lynn; Chee, Michael W L (2023-04-12). "Influence of mid-afternoon nap duration and sleep parameters on memory encoding, mood, processing speed, and vigilance" (in en). Sleep 46 (4). doi:10.1093/sleep/zsad025. ISSN 0161-8105. PMID 36775965. 
  25. ↑ 25.0 25.1 "Napping May Not Be Such a No-No" (in en). 2009-11-01. https://www.health.harvard.edu/newsletter_article/napping-may-not-be-such-a-no-no. 
  26. ↑ 26.0 26.1 "Sleep-wake patterns and subjective sleep quality of day and night workers: interaction between napping and main sleep episodes". Sleep 12 (5): 439–448. October 1989. doi:10.1093/sleep/12.5.439. PMID 2799217. 
  27. ↑ "Role of Napping for Learning across the Lifespan". Current Sleep Medicine Reports 6 (4): 290–297. December 2020. doi:10.1007/s40675-020-00193-9. PMID 33816064. 
  28. ↑ 28.0 28.1 28.2 "The role of prescribed napping in sleep medicine". Sleep Medicine Reviews 7 (3): 227–35. June 2003. doi:10.1053/smrv.2002.0241. PMID 12927122. 
  29. ↑ "Narcolepsy and idiopathic hypersomnolence". Clinics in Chest Medicine 19 (1): 169–81. March 1998. doi:10.1016/s0272-5231(05)70440-8. PMID 9554226. 
  30. ↑ 30.0 30.1 Mantua, Janna; Spencer, Rebecca M.C. (September 2017). "Exploring the nap paradox: are mid-day sleep bouts a friend or foe?" (in en). Sleep Medicine 37: 88–97. doi:10.1016/j.sleep.2017.01.019. PMID 28899546. 
  31. ↑ "Are you awake? Cognitive performance and reverie during the hypnopompic state.". Sleep and Cognition.. Washington, DC: American Psychological Society. 1990. pp. 159–175. doi:10.1037/10499-012. ISBN 1-55798-083-7. 
  32. ↑ "Sleep inertia". Sleep Medicine Reviews 4 (4): 341–353. August 2000. doi:10.1053/smrv.2000.0098. PMID 12531174. 
  33. ↑ 33.0 33.1 "J-curve relation between daytime nap duration and type 2 diabetes or metabolic syndrome: A dose-response meta-analysis". Scientific Reports 6 (1). December 2016. doi:10.1038/srep38075. PMID 27909305. Bibcode: 2016NatSR...638075Y. 
  34. ↑ "Exploring the nap paradox: are mid-day sleep bouts a friend or foe?". Sleep Medicine 37: 88–97. September 2017. doi:10.1016/j.sleep.2017.01.019. PMID 28899546. 
  35. ↑ Simon, Katharine C.; Cadle, Chelsea; Shuster, Alessandra E.; Malerba, Paola (2025-02-05). "Sleep Across the Lifespan: A Neurobehavioral Perspective" (in en). Current Sleep Medicine Reports 11 (1): 7. doi:10.1007/s40675-025-00322-2. ISSN 2198-6401. 
  36. ↑ Colrain, Ian M.; Baker, Fiona C. (March 2011). "Changes in Sleep as a Function of Adolescent Development" (in en). Neuropsychology Review 21 (1): 5–21. doi:10.1007/s11065-010-9155-5. ISSN 1040-7308. PMID 21225346. 
  37. ↑ Bruce, Ellen S; Lunt, Laura; McDonagh, Janet E (October 2017). "Sleep in adolescents and young adults" (in en). Clinical Medicine 17 (5): 424–428. doi:10.7861/clinmedicine.17-5-424. PMID 28974591. 
  38. ↑ Kim, Minjung; Um, Yoo-Hyun; Kim, Tae-Won; Kim, Sung-Min; Seo, Ho-Jun; Jeong, Jong-Hyun; Lee, Jihyung; Kim, Suhyung et al. (2021-12-31). "Association Between Age and Sleep Quality: Findings From a Community Health Survey" (in English). Sleep Medicine Research 12 (2): 155–160. doi:10.17241/smr.2021.01158. ISSN 2093-9175. https://www.sleepmedres.org/journal/view.php?number=193. 
  39. ↑ Souabni, Maher; Souabni, Mehdi J.; Hammouda, Omar; Romdhani, Mohamed; Trabelsi, Khaled; Ammar, Achraf; Driss, Tarak (2022-10-21). "Benefits and risks of napping in older adults: A systematic review" (in English). Frontiers in Aging Neuroscience 14. doi:10.3389/fnagi.2022.1000707. ISSN 1663-4365. PMID 36337699. 
  40. ↑ Casagrande, Maria; Forte, Giuseppe; Favieri, Francesca; Corbo, Ilaria (2022-07-11). "Sleep Quality and Aging: A Systematic Review on Healthy Older People, Mild Cognitive Impairment and Alzheimer's Disease" (in en). International Journal of Environmental Research and Public Health 19 (14): 8457. doi:10.3390/ijerph19148457. ISSN 1660-4601. PMID 35886309. 
  41. ↑ "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. June 2009. doi:10.1111/j.1365-2869.2008.00718.x. PMID 19645971. 
  42. ↑ "Napping Behavior in Adolescents: Consensus, Dissents, and Recommendations" (in en). Sleep and Vigilance 5 (2): 189–196. 2021-07-28. doi:10.1007/s41782-021-00155-3. ISSN 2510-2265. 
  43. ↑ "How to interpret the results of a sleep study". Journal of Community Hospital Internal Medicine Perspectives 4 (5). January 2014. doi:10.3402/jchimp.v4.24983. PMID 25432643. 
  44. ↑ "Ultimate Napping: A How-To Guide" (in en). Psychology Today. 5 June 2010. https://www.psychologytoday.com/intl/blog/minding-the-body/201006/ultimate-napping-how-guide. 

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