A nap is commonly described as a short-sleep or more precisely a sleep which is distinct and shorter than an individual’s routine sleep cycle.1 The practice of taking naps is widely accepted throughout the world. Napping or day-time sleep is regarded as normal routine in infants and young adolescents.
A survey conducted by National Sleep Foundation USA in 2008, recorded that 46% of the respondents took at least two naps in one month with an average duration of approximately one-hour.2
This article mainly focuses on the types of naps, its ideal timing and duration along with its pros and cons on night time sleep and overall health.
Types of napping or daytime sleep:
Different individuals choose nap/daytime napping for several reasons. Some of the reasons include:
- Replacement napping: This is for many individuals the practical solution to sleepiness. These are also known as compensatory naps. This type of napping is most common among the shift workers or the individuals suffering from sleep disorders.
- Prophylactic napping: This kind of napping happens for an expected sleep loss, or to avoid the feeling of tiredness or sleepiness later on. This type of napping pattern is more common with night shift workers specifically before the starting of extended shifts.
- Appetitive napping: This is also known as recreational napping. For many individuals this has been reported as a sleep due to boredom or for an enjoyment or out of habit.
Nap length and timing
The ideal time for a nap or daytime sleep is post lunch period around 3.00 pm. Post lunch sleepiness can occur whether the lunch is consumed or not. The biological basis for daytime naps is that during the afternoon timings a decline in arousal levels is observed. It happens as a part of biological rhythm such as circadian rhythm. As afternoon is the midpoint of the day, a short nap in the post lunch time can improve functional ability for the rest of the day.3Lovato N et al. (2010) also documented from research that naps taken in the post lunch period i.e. between 2 to 4pm have increased recovery value than the morning and evening naps.1
Several studies have been conducted to determine the ideal duration of nap needed to restore performance with minimal effects of sleep inertia.4 In the summary of literature, it was concluded that nap duration varies from 30 to 90 minutes in subjects with different age groups.5 Brooks A, et al. (2006) compared the benefits of different nap lengths relative to no nap at all. They observed the benefits of nap lengths of 5,10,20 minutes. It was found that 10 minute nap was the most effective length for an afternoon power nap in improving the sleep latency, subjective sleeplessness, fatigue, and cognitive performance.6
Pros and Cons of napping
A number of studies have documented that napping leads to subjective and behavioural improvements.
Naps as counter-measure to sleepiness: several studies have explored the benefits of napping in comparison to other counter-measures such as caffeine and stimulant medicine. Most of the literature recorded beneficial effects of napping in cognitive functioning, improved learning and enhanced reaction time as compared to other counter-measures to sleepiness. Bonnet MH, et al. 1995 correlated the effects of nap to those of caffeine and concluded that the napping advantages in comparison to caffeine effects were more balanced and long lasting.7
Reduced fatigue and Increased vigilance: daytime sleep or naps containing stage 1 or 2 of seep cycle helps in improving the performance and reducing the fatigue. Hayashi M, et al. (2005) recorded a decreased performance and alertness in the absence of post-lunch nap.8
Improved mood: A short midday nap can reduce the subsequent sleepiness and can elevate and enhance the negative mood. A study by Ru T, et al. (2017) reported that a short midday nap has significant effects on alertness and subtly benefited the mood of the subjects. A significant reduction in negative mood was observed not throughout the test but after taking a nap. Hence, it is safe to say that a midday nap/ daytime sleep can help elevate the fatigue, tiredness and negative mood.9
Enhanced cognitive performance: A short midday nap can significantly improve the higher executive or cognitive function and performance of an individual. Ru Toata, et al. (2017) suggested that a short nap can significantly improve the participants accuracy for both easy and difficult tasks.9 Similarly, Kaida K, et al. (2012) revealed that a short daytime nap can significantly improve the reaction time in visual tasks.10 Another study by Takahashi M and Arito H. (2000) also suggested that a short nap helps in improving the subject’s performance and logical reasoning.11
Better memory: The degree of declarative memory is related to slow wave sleep (SWS) in the nap. Short naps or daytime sleep is associated with the improvement in memory. Tucker MA, et al. (2006) also confirmed that memory is related to sleep architecture and daytime nap helps to improve declarative memory.12
In older adults: With advancing age, the sleepiness increases and the older individuals have more opportunities to sleep, it is more likely that napping is both more frequent and perhaps more beneficial for older group. Tanaka H, et al. (2001, 2002) studied the impact of napping on overall health and well being of older individuals. It was documented that a combination of 30 minutes sleep and moderate intensity workout in the evening improves the overall sleep architecture, quality and reduced the subjective daytime sleepiness.13,14 Tanaka H and shirakarna S. (2004) found that short naps and moderate workouts not only helps in improvements in sleep but also enhances the performance of verbal memory tests in older adults.15
Sleep inertia: A transitional state between sleep and wake is known as sleep inertia. It is generally associated with impaired performance, reduced awareness and a will to go back to sleep. The intensity and duration of sleep inertia may vary and can last from minutes to hours depending upon the situational factors.16 Daytime sleep is mostly followed by a phase of sleep inertia. It causes impaired vigilance and performance for approximately 30 minutes after awakening. The intensity and duration of sleep inertia varies with the timing and duration of nap. It also depends on the phase of sleep in which awakening happens.
The intensity of sleep inertia is more severe if the individual takes longer naps and awakens from deep NON-REM sleep. The occurrence and intensity can be reduced either by taking naps shorter than 20 minutes to avoid awakening in NON-REM sleep cycle or by taking a nap of approximately 90 minutes to manage time for one NON-REM cycle an waking in REM sleep.3
Effects of napping on night-time sleep: Another adverse effect of concern about daytime naps is that it could interfere with the quality of the sleep at night. Ye L, et al. (2014) evaluated the relation between the habit of napping and its effect on the night-time sleep in college going young adults. It was observed that individuals with self-reported frequent, long and late nappers have higher risk of disrupted night-time sleep and more severe sleep deprivation.17 The substantial slow sleep wave containing longer durations of napping also disrupts the duration and quality of the subsequent night-time sleep.1
Together with earlier and current literature, we can conclude that a mid-day/day-time/post-lunch or a short nap helps in reducing fatigue, relaxing mind along with elevating the mood and improving cognitive performance. Though with all the beneficial effects of a short nap, it is important to consider that individual factors such as age, gender, different napping behaviors, timing of the nap, duration and the reasons for a short nap also modulate the benefits and adverse effects of the short naps.
- Lovato N, Lack L. The effects of napping on cognitive functioning. Prog Brain Res. 2010; 185:155-166.
- Milner CE, Cote KA. Benefits of napping in healthy adults: impact of nap length, time of day, age, and experience with napping. J Sleep Res. 2009;18(2):272-281.
- Dhand R, Sohal H. Good sleep, bad sleep! The role of daytime naps in healthy adults. Curr Opin Pulm Med. 2006;12(6):379-382.
- Milner CE, Cote KA. A dose‐response investigation of the benefits of napping in healthy young, middle‐aged and older adults. Sleep Biol. Rhythms, 2008, 6(1): 2-15
- Pilcher JJ, Michalowski KR, Carrigan RD. The prevalence of daytime napping and its relationship to nighttime sleep. Behav Med. 2001;27(2):71-76.
- Brooks A, Lack L. A brief afternoon nap following nocturnal sleep restriction: which nap duration is most recuperative? Sleep. 2006;29(6):831-840.
- Bonnet MH, Gomez S, Wirth O, Arand DL. The use of caffeine versus prophylactic naps in sustained performance.
- Hayashi M, Motoyoshi N, Hori T. Recuperative power of a short daytime nap with or without stage 2 sleep. Sleep. 2005;28(7):829-836.
- Ru T, Chen Q, You J, Zhou G. Effects of a short midday nap on habitual nappers’ alertness, mood and mental performance across cognitive domains. J Sleep Res. 2019;28(3)
- Kaida K, Takeda Y, Tsuzuki K. Can a short nap and bright light function as implicit learning and visual search enhancers? Ergonomics. 2012;55(11):1340-1349
- Takahashi M, Arito H. Maintenance of alertness and performance by a brief nap after lunch under prior sleep deficit. Sleep. 2000;23(6):813-819.
- Tucker MA, Hirota Y, Wamsley EJ, Lau H, Chaklader A, Fishbein W. A daytime nap containing solely non-REM sleep enhances declarative but not procedural memory. Neurobiol Learn Mem. 2006;86(2):241-247.
- Tanaka H, Taira K, Arakawa M, et al. Effects of short nap and exercise on elderly people having difficulty in sleeping. Psychiatry Clin Neurosci. 2001;55(3):173-174.
- Tanaka H, Taira K, Arakawa M, et al. Short naps and exercise improve sleep quality and mental health in the elderly. Psychiatry Clin Neurosci. 2002;56(3):233-234.
- Tanaka H, Shirakawa S. Sleep health, lifestyle and mental health in the Japanese elderly: ensuring sleep to promote a healthy brain and mind. J Psychosom Res. 2004;56(5):465-477.
- Trotti LM. Waking up is the hardest thing I do all day: Sleep inertia and sleep drunkenness. Sleep Med Rev. 2017; 35:76-84.
- Ye L, Hutton Johnson S, Keane K, Manasia M, Gregas M. Napping in college students and its relationship with nighttime sleep. J Am Coll Health. 2015;63(2):88-97.