:Nap

Naps can be categorized based on their purpose and duration {{Cite news |date=2022-12-13 |title=What Are the Different Types of Naps? |url=https://sleepdoctor.com/napping/types-of-naps |archive-url=http://web.archive.org/web/20250119222516/https://sleepdoctor.com/napping/types-of-naps/ |archive-date=2025-01-19 |access-date=2025-03-16 |work=Sleep Doctor |language=en-US}}

• 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.{{Cite journal |last1=Caldwell |first1=John A. |last2=Mallis |first2=Melissa M. |last3=Caldwell |first3=J. Lynn |last4=Paul |first4=Michel A. |last5=Miller |first5=James C. |last6=Neri |first6=David F. |last7=Aerospace Medical Association Fatigue Countermeasures Subcommittee of the Aerospace Human Factors Committee |date=January 2009 |title=Fatigue countermeasures in aviation |url=https://pubmed.ncbi.nlm.nih.gov/19180856/ |journal=Aviation, Space, and Environmental Medicine |volume=80 |issue=1 |pages=29–59 |doi=10.3357/asem.2435.2009 |issn=0095-6562 |pmid=19180856}}{{Cite journal |last1=Sieberichs |first1=Sebastian |last2=Kluge |first2=Annette |date=September 2018 |title=Effects of In-Flight Countermeasures to Mitigate Fatigue Risks in Aviation |url=https://econtent.hogrefe.com/doi/10.1027/2192-0923/a000143 |journal=Aviation Psychology and Applied Human Factors |volume=8 |issue=2 |pages=86–92 |doi=10.1027/2192-0923/a000143 |issn=2192-0923}}
• 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.{{Cite journal |last1=Vizmanos |first1=Barbara |last2=Cascales |first2=Ana Isabel |last3=Rodríguez-Martín |first3=María |last4=Salmerón |first4=Diego |last5=Morales |first5=Eva |last6=Aragón-Alonso |first6=Aurora |last7=Scheer |first7=Frank A. J. L. |last8=Garaulet |first8=Marta |date=2023 |title=Lifestyle mediators of associations among siestas, obesity, and metabolic health |url=https://onlinelibrary.wiley.com/doi/10.1002/oby.23765 |journal=Obesity |language=en |volume=31 |issue=5 |pages=1227–1239 |doi=10.1002/oby.23765 |pmid=37140401 |issn=1930-739X|doi-access=free }}
• 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.  {{Cite journal |last1=Reyner |first1=L. A. |last2=Horne |first2=J. A. |date=November 1997 |title=Suppression of sleepiness in drivers: combination of caffeine with a short nap |url=https://pubmed.ncbi.nlm.nih.gov/9401427/ |journal=Psychophysiology |volume=34 |issue=6 |pages=721–725 |doi=10.1111/j.1469-8986.1997.tb02148.x |issn=0048-5772 |pmid=9401427}}
• Essential Nap: During times of illness or when in need of recovery, essential naps are taken to support healing and boost the immune system.{{Cite journal |last1=Lange |first1=Tanja |last2=Dimitrov |first2=Stoyan |last3=Born |first3=Jan |date=April 2010 |title=Effects of sleep and circadian rhythm on the human immune system |url=https://pubmed.ncbi.nlm.nih.gov/20398008/ |journal=Annals of the New York Academy of Sciences |volume=1193 |issue=1 |pages=48–59 |doi=10.1111/j.1749-6632.2009.05300.x |issn=1749-6632 |pmid=20398008|bibcode=2010NYASA1193...48L }}{{Cite journal |last1=Besedovsky |first1=Luciana |last2=Lange |first2=Tanja |last3=Born |first3=Jan |date=January 2012 |title=Sleep and immune function |journal=Pflügers Archiv: European Journal of Physiology |volume=463 |issue=1 |pages=121–137 |doi=10.1007/s00424-011-1044-0 |issn=1432-2013 |pmc=3256323 |pmid=22071480}}

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.{{Cite web |last=thensf |date=2021-10-30 |title=What is Microsleep? |url=https://www.thensf.org/what-is-microsleep/ |access-date=2025-03-17 |website=National Sleep Foundation |language=en-US}}

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.{{Cite journal |last1=Lastella |first1=Michele |last2=Halson |first2=Shona L. |last3=Vitale |first3=Jacopo A. |last4=Memon |first4=Aamir R. |last5=Vincent |first5=Grace E. |date=2021-06-24 |title=To Nap or Not to Nap? A Systematic Review Evaluating Napping Behavior in Athletes and the Impact on Various Measures of Athletic Performance |journal=Nature and Science of Sleep |language=English |volume=13 |pages=841–862 |doi=10.2147/NSS.S315556|doi-access=free |pmid=34194254 |pmc=8238550 }} 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.{{Cite journal |date=1987-07-01 |title=Temporal Placement of a Nap for Alertness: Contributions of Circadian Phase and Prior Wakefulness |journal=Sleep |doi=10.1093/sleep/10.4.313 |issn=1550-9109 |doi-access=free}}

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.{{Cite journal |last1=Rosekind |first1=Mark R. |last2=Graeber |first2=R. Curtis |last3=Dinges |first3=David F. |last4=Connell |first4=Linda J. |last5=Rountree |first5=Michael S. |last6=Spinweber |first6=Cheryl L. |last7=Gillen |first7=Kelly A. |date=1994-09-01 |title=Crew factors in flight operations 9: Effects of planned cockpit rest on crew performance and alertness in long-haul operations |url=https://ntrs.nasa.gov/citations/19950006379 |language=en}}

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.{{Cite journal |last1=Stepan |first1=Michelle E. |last2=Altmann |first2=Erik M. |last3=Fenn |first3=Kimberly M. |date=2021-11-12 |title=Slow-wave sleep during a brief nap is related to reduced cognitive deficits during sleep deprivation |journal=Sleep |volume=44 |issue=11 |pages=zsab152 |doi=10.1093/sleep/zsab152 |issn=1550-9109 |pmc=8598175 |pmid=34156468}} 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.{{Citation |last1=Patel |first1=Aakash K. |title=Physiology, Sleep Stages |date=2025 |work=StatPearls |url=https://www.ncbi.nlm.nih.gov/books/NBK526132/ |access-date=2025-03-17 |place=Treasure Island (FL) |publisher=StatPearls Publishing |pmid=30252388 |last2=Reddy |first2=Vamsi |last3=Shumway |first3=Karlie R. |last4=Araujo |first4=John F.}}

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.{{cite journal |vauthors=Mednick SC, Cai DJ, Kanady J, Drummond SP |date=November 2008 |title=Comparing the benefits of caffeine, naps and placebo on verbal, motor and perceptual memory |journal=Behavioural Brain Research |volume=193 |issue=1 |pages=79–86 |doi=10.1016/j.bbr.2008.04.028 |pmc=2603066 |pmid=18554731}}

Research suggests that shorter, habitual naps after instruction offer the most benefits to learning.{{cite journal |vauthors=Lemos N, Weissheimer J, Ribeiro S |date=2014-06-03 |title=Naps in school can enhance the duration of declarative memories learned by adolescents |journal=Frontiers in Systems Neuroscience |volume=8 |pages=103 |doi=10.3389/fnsys.2014.00103 |pmc=4042263 |pmid=24917794 |doi-access=free}}{{cite journal |vauthors=Ji X, Li J, Liu J |date=February 2018 |title=The Relationship Between Midday Napping And Neurocognitive Function in Early Adolescents |journal=Behavioral Sleep Medicine |volume=17 |issue=5 |pages=537–551 |doi=10.1080/15402002.2018.1425868 |pmc=6669094 |pmid=29388804}} 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.{{cite journal |vauthors=Takahashi M, Nakata A, Haratani T, Ogawa Y, Arito H |date=July 2004 |title=Post-lunch nap as a worksite intervention to promote alertness on the job |journal=Ergonomics |volume=47 |issue=9 |pages=1003–1013 |doi=10.1080/00140130410001686320 |pmid=15204275 |s2cid=37556310}} Napping enhances alertness in young adults and adolescents during afternoons’ performances, which affect efficiency.{{cite journal |vauthors=Takahashi M, Fukuda H, Arito H |date=July 1998 |title=Brief naps during post-lunch rest: effects on alertness, performance, and autonomic balance |journal=European Journal of Applied Physiology and Occupational Physiology |volume=78 |issue=2 |pages=93–98 |doi=10.1007/s004210050392 |pmid=9694306 |s2cid=2601267}} 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.{{cite journal |vauthors=Tietzel AJ, Lack LC |date=September 2002 |title=The recuperative value of brief and ultra-brief naps on alertness and cognitive performance |journal=Journal of Sleep Research |volume=11 |issue=3 |pages=213–218 |doi=10.1046/j.1365-2869.2002.00299.x |pmid=12220317 |s2cid=22706866}}

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.{{cite journal |vauthors=Tucker MA, Hirota Y, Wamsley EJ, Lau H, Chaklader A, Fishbein W |date=September 2006 |title=A daytime nap containing solely non-REM sleep enhances declarative but not procedural memory |journal=Neurobiology of Learning and Memory |volume=86 |issue=2 |pages=241–247 |doi=10.1016/j.nlm.2006.03.005 |pmid=16647282 |s2cid=17606945}}

In adults, a causal association has been found between habitual daytime napping and larger brain volume.{{cite journal |vauthors=Paz V, Dashti HS, Garfield V |year=2023 |title=Is there an association between daytime napping, cognitive function, and brain volume? A Mendelian randomization study in the UK Biobank |journal=Sleep Health |volume=9 |issue=5 |pages=786–793 |doi=10.1016/j.sleh.2023.05.002 |pmid=37344293}} Brain volume normally declines with age, and is associated with neurodegenerative disease. Earlier studies have shown benefits of napping for cognitive performance for healthy adults.

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.{{Cite journal |last1=Leong |first1=Ruth L F |last2=Lau |first2=TeYang |last3=Dicom |first3=Andrew R |last4=Teo |first4=Teck Boon |last5=Ong |first5=Ju Lynn |last6=Chee |first6=Michael W L |date=2023-04-12 |title=Influence of mid-afternoon nap duration and sleep parameters on memory encoding, mood, processing speed, and vigilance |journal=Sleep |language=en |volume=46 |issue=4 |doi=10.1093/sleep/zsad025 |issn=0161-8105 |pmc=10091091 |pmid=36775965}} Twenty- to thirty-minute naps are recommended for adults, while young children and elderly people may need longer naps.{{Cite web |date=2009-11-01 |title=Napping May Not Be Such a No-No |url=https://www.health.harvard.edu/newsletter_article/napping-may-not-be-such-a-no-no |access-date=2023-02-18 |website=Harvard Health |language=en}}{{cite journal |vauthors=Chan OY, Phoon WH, Gan SL, Ngui SJ |date=October 1989 |title=Sleep-wake patterns and subjective sleep quality of day and night workers: interaction between napping and main sleep episodes |journal=Sleep |volume=12 |issue=5 |pages=439–448 |doi=10.1093/sleep/12.5.439 |pmid=2799217 |doi-access=free}} Research, on the other hand, has shown that the benefits of napping depend on sleep onset and sleep phases rather than time and duration.{{cite journal |vauthors=Jones BJ, Spencer RM |date=December 2020 |title=Role of Napping for Learning across the Lifespan |journal=Current Sleep Medicine Reports |volume=6 |issue=4 |pages=290–297 |doi=10.1007/s40675-020-00193-9 |pmc=8011550 |pmid=33816064}}

It has been shown that excessive daytime sleepiness (EDS) can be improved by prescribed napping in narcolepsy.{{cite journal |vauthors=Takahashi M |date=June 2003 |title=The role of prescribed napping in sleep medicine |journal=Sleep Medicine Reviews |volume=7 |issue=3 |pages=227–35 |doi=10.1053/smrv.2002.0241 |pmid=12927122}} Apart from narcolepsy, it has not been demonstrated that naps are beneficial for EDS in other sleep disorders. For idiopathic hypersomnia, patients typically experience sleep inertia and are unrefreshed after napping.{{cite journal |vauthors=Choo KL, Guilleminault C |date=March 1998 |title=Narcolepsy and idiopathic hypersomnolence |journal=Clinics in Chest Medicine |volume=19 |issue=1 |pages=169–81 |doi=10.1016/s0272-5231(05)70440-8 |pmid=9554226 |doi-access=free}}

For healthy individuals in need of cognitive or emotional improvement, prescribed naps may be beneficial.{{Cite journal |last1=Mantua |first1=Janna |last2=Spencer |first2=Rebecca M.C. |date=September 2017 |title=Exploring the nap paradox: are mid-day sleep bouts a friend or foe? |journal=Sleep Medicine |language=en |volume=37 |pages=88–97 |doi=10.1016/j.sleep.2017.01.019 |pmc=5598771 |pmid=28899546}} However, excessive napping, especially in adults with other health conditions, may be linked with negative outcomes and should be approached holistically and with caution.

The state of grogginess, impaired cognition and disorientation experienced when awakening from sleep is known as sleep inertia.{{cite book |title=Sleep and Cognition. |vauthors=Dinges DF |date=1990 |publisher=American Psychological Society |isbn=1-55798-083-7 |veditors=Bootzin R, Kihlstrom J, Schacter D |location=Washington, DC |pages=159–175 |chapter=Are you awake? Cognitive performance and reverie during the hypnopompic state. |doi=10.1037/10499-012}} This state reduces the speed of cognitive tasks but has no effects on the accuracy of task performance. The effects of sleep inertia rarely last longer than 30 minutes in the absence of prior sleep deprivation.{{cite journal |vauthors=Tassi P, Muzet A |date=August 2000 |title=Sleep inertia |journal=Sleep Medicine Reviews |volume=4 |issue=4 |pages=341–353 |doi=10.1053/smrv.2000.0098 |pmid=12531174}}

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.{{cite journal |vauthors=Yamada T, Shojima N, Yamauchi T, Kadowaki T |date=December 2016 |title=J-curve relation between daytime nap duration and type 2 diabetes or metabolic syndrome: A dose-response meta-analysis |journal=Scientific Reports |volume=6 |issue=1 |pages=38075 |bibcode=2016NatSR...638075Y |doi=10.1038/srep38075 |pmc=5133463 |pmid=27909305}} 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.

Habitual naps are also an indicator of neurological degradation such as dementia in the elderly, as reduction in brain function causes more sleepiness.{{cite journal |vauthors=Mantua J, Spencer RM |date=September 2017 |title=Exploring the nap paradox: are mid-day sleep bouts a friend or foe? |journal=Sleep Medicine |volume=37 |pages=88–97 |doi=10.1016/j.sleep.2017.01.019 |pmc=5598771 |pmid=28899546}}

The need and benefits of napping vary across different age groups since sleep patterns and requirements across a person’s lifespan vary with time.{{Cite journal |last1=Simon |first1=Katharine C. |last2=Cadle |first2=Chelsea |last3=Shuster |first3=Alessandra E. |last4=Malerba |first4=Paola |date=2025-02-05 |title=Sleep Across the Lifespan: A Neurobehavioral Perspective |url=https://link.springer.com/article/10.1007/s40675-025-00322-2 |journal=Current Sleep Medicine Reports |language=en |volume=11 |issue=1 |pages=7 |doi=10.1007/s40675-025-00322-2 |issn=2198-6401|doi-access=free }}

• 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.{{Cite journal |last1=Colrain |first1=Ian M. |last2=Baker |first2=Fiona C. |date=March 2011 |title=Changes in Sleep as a Function of Adolescent Development |journal=Neuropsychology Review |language=en |volume=21 |issue=1 |pages=5–21 |doi=10.1007/s11065-010-9155-5 |issn=1040-7308 |pmc=7543715 |pmid=21225346}}{{Cite journal |last1=Bruce |first1=Ellen S |last2=Lunt |first2=Laura |last3=McDonagh |first3=Janet E |date=October 2017 |title=Sleep in adolescents and young adults |journal=Clinical Medicine |language=en |volume=17 |issue=5 |pages=424–428 |doi=10.7861/clinmedicine.17-5-424 |pmc=6301929 |pmid=28974591}}
• 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,{{Cite journal |last1=Kim |first1=Minjung |last2=Um |first2=Yoo-Hyun |last3=Kim |first3=Tae-Won |last4=Kim |first4=Sung-Min |last5=Seo |first5=Ho-Jun |last6=Jeong |first6=Jong-Hyun |last7=Lee |first7=Jihyung |last8=Kim |first8=Suhyung |last9=Cho |first9=In Hee |last10=Kim |first10=Suk-Young |last11=Hong |first11=Seung-Chul |date=2021-12-31 |title=Association Between Age and Sleep Quality: Findings From a Community Health Survey |url=https://www.sleepmedres.org/journal/view.php?number=193 |journal=Sleep Medicine Research |language=English |volume=12 |issue=2 |pages=155–160 |doi=10.17241/smr.2021.01158 |issn=2093-9175|doi-access=free }} 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.{{Cite journal |last1=Souabni |first1=Maher |last2=Souabni |first2=Mehdi J. |last3=Hammouda |first3=Omar |last4=Romdhani |first4=Mohamed |last5=Trabelsi |first5=Khaled |last6=Ammar |first6=Achraf |last7=Driss |first7=Tarak |date=2022-10-21 |title=Benefits and risks of napping in older adults: A systematic review |journal=Frontiers in Aging Neuroscience |language=English |volume=14 |doi=10.3389/fnagi.2022.1000707 |doi-access=free |pmid=36337699 |pmc=9634571 |issn=1663-4365}}{{Cite journal |last1=Casagrande |first1=Maria |last2=Forte |first2=Giuseppe |last3=Favieri |first3=Francesca |last4=Corbo |first4=Ilaria |date=2022-07-11 |title=Sleep Quality and Aging: A Systematic Review on Healthy Older People, Mild Cognitive Impairment and Alzheimer's Disease |journal=International Journal of Environmental Research and Public Health |language=en |volume=19 |issue=14 |pages=8457 |doi=10.3390/ijerph19148457 |doi-access=free |pmid=35886309 |pmc=9325170 |issn=1660-4601 }}

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.{{cite journal | vauthors = Milner CE, Cote KA | title = Benefits of napping in healthy adults: impact of nap length, time of day, age, and experience with napping | journal = Journal of Sleep Research | volume = 18 | issue = 2 | pages = 272–281 | date = June 2009 | pmid = 19645971 | doi = 10.1111/j.1365-2869.2008.00718.x | s2cid = 22815227 }} Sleep inertia is less intense after short naps.{{Cite journal | vauthors = Santos JS, Beijamini F, Louzada FM |date=2021-07-28 |title=Napping Behavior in Adolescents: Consensus, Dissents, and Recommendations |journal=Sleep and Vigilance |language=en |volume=5 |issue=2 |pages=189–196 |doi=10.1007/s41782-021-00155-3 |s2cid=237714078 |issn=2510-2265}} Sleep latency is shorter when a nap is taken between 3 and 5 pm, compared with a nap taken between 7 and 9 pm.{{cite journal | vauthors = Shrivastava D, Jung S, Saadat M, Sirohi R, Crewson K | title = How to interpret the results of a sleep study | journal = Journal of Community Hospital Internal Medicine Perspectives | volume = 4 | issue = 5 | pages = 24983 | date = January 2014 | pmid = 25432643 | pmc = 4246141 | doi = 10.3402/jchimp.v4.24983 }}

According to The Sleep Foundation, Psychology Today and Harvard Health Publishing, these are the best practices for napping:{{Cite web | vauthors = Andrews LW | date = 5 June 2010 |title=Ultimate Napping: A How-To Guide | work = Psychology Today |url=https://www.psychologytoday.com/intl/blog/minding-the-body/201006/ultimate-napping-how-guide |access-date=2023-02-18 |language=en}}

• 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

• Siesta - a short nap in the early afternoon, often after the midday meal.
• Sleep Hygiene
• Microsleep
• Power Nap

{{Reflist}}

{{Commons category|Napping}}

• {{cite web | url = https://archive.boston.com/bostonglobe/ideas/naps/ | title = How to nap | work = Sunday Ideas section | publisher = The Boston Globe | date = 14 June 2008 | access-date = 16 June 2009 }}
• {{cite web | url = https://www.theguardian.com/lifeandstyle/2009/jan/27/napping-guide-health-wellbeing | title = Napping: the expert's guide | work = The Guardian | date = 27 January 2009 | access-date = 16 June 2009 }}

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Category:Sleep

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