To sleep during the day, perchance to restore clarity of mind? This is a subject of ongoing scientific research.  Napping is viewed by many as a compensatory restorative process due to poor sleep the night before or for mitigating daytime somnolence.  Studies have demonstrated that partial acute or chronic sleep deprivation at night leads to errors in thinking, mathematical calculations and erosion of working memory – the ability to hold information on our mental screen and act upon it.

Recent research (Ong et al, published in the journal SLEEP, September 2020) suggests that a nap of an hour and a half, intervening between learning a simple word association task and then being tested,   facilitated performance, compared to a control group learning the same task without the intervening nap period. PSG and fMRI data suggest enhanced hippocampal activation in those who had napped, which may be a biomarker for uploading of encoded neural data to neo-cortical networks.  Slow brain waves may reflect this process, while spindle wave forms measured during naps may be correlated with calcium-dependent synaptic potentiation and alterations in gene expression in cortical neurons.

Excessive napping could potentially interfere with sleep onset at night. Long naps during the day (90 minute or more) could potentially disrupt the continuity of sleep at night, although non-habitual nap behavior has been associated with performance gains in specific, daytime administered long-term memory challenges.  (cf. Leong et al. SLEEP, December 2020).

Workplace wellness studies have suggested that when employers support employees’ sleep hygiene practices, including strategic naps prior to or during the work shift, modest gains in sleep duration and quality and reduction in diurnal sleepiness have been noted.  However, the value of napping may hinge on the time of day when the nap occurs. Not uncommonly, individuals working the day shift experience a mid-afternoon nadir of energy or mood, that may be addressed with a short nap (e.g. 45 minutes or less) instead of consuming caffeine or processed and sugar laden foods. There is a characteristic dip in the circadian driving mechanism in the hours after lunch, which is not strictly related to post-prandial carb intake.  Some people are compelled to rest their eyes and push away from their screen while other folks feel a pressure to nap.

Nighttime sleep fragmentation and reduced Slow Wave Sleep are common among those age 70 and older. Frequent cat napping at intervals is used as a coping strategy, but the downside is the feeling of not being rested upon awakening in the morning.  Continuous wakefulness creates a homeostatic sleep pressure. This biological press to sleep builds throughout the day toward a crescendo at night, hopefully translating into a fairly rapid  onset of slumber. Unfortunately, over-indulgence in daytime napping, perhaps a response to boredom, loneliness or prolonged COVID-19 confinement could take the wind out of the homeostatic sails and make it harder to initiate, or maintain, sleep. This may particularly be the case for the elderly and sedentary types, and becomes a vicious cycle of daytime nodding off  followed by tossing and turning in the darkness of night. This process invites next-day mental fatigue and fog, low energy levels and irritability.

Elderly folks take a variety of medications, some of which have daytime sedating side-effects, leading to irresistible urges to sleep at the wrong times of day. Seeking medical advice from a sleep specialist

regarding the use of sleep medicines is valuable. Care needs to be taken in seniors or other sub-groups at risk for falls or dementia if hypnotic medication is prescribed as a compensatory strategy for poor nocturnal sleep.

Severe sleep disorders, such as narcolepsy, often involve affected individuals taking frequent rest and nap periods during the day. Rapid descent into deep sleep may occur. Narcolepsy requires complex pharmacologic and behavioral management, but some data suggest that helping the narcoleptic overcome sleep inertia in the morning (the strong desire to stay in bed and slumber) and stabilizing nighttime sleep schedules may lead to reduced napping and more efficient functioning during the day.

Napping is clearly a complex and nuanced issue. In general, achieving adequate nocturnal sleep (7-8 hours for adults, 9-10 hours for teens) optimizes central information processing (viz., verbal learning, math calculation skills and working memory capacity) as well as self-regulation through pruning of synaptic networks occurring during sleep.  This writer’s experience has been that achieving a steady 8 hours of shut-eye nightly has greatly diminished the need for short mid-afternoon naps.

Honoring our homeostatic sleep pressure and our circadian flow of peaks and valleys permits more strategic and efficient napping or intentional disconnect from work activities for quick restoration of concentration and energy levels, and reduction of eye fatigue or strain. Kindergarten and pre-school educators have long understood the importance of a scheduled nap in the afternoon for the still developing central nervous systems of young children and their receptivity to new learning.  The bottom line is that, absent any co-morbid medical or psychological impairment, feeling a strong need to nap regularly and for prolonged periods every day (>90 minutes) to counter excessive mental fatigue or energy depletion, begs a look at tweaking one’s nocturnal sleep habits.

REFERENCES:

Leong, R.L.F., Yu, N., Ong, J.L., Ng, A.S.C., Jamaluddin, S.A., Cousins, J.N., Chee, N.Y.N., Chee M.W.L. (2020). Memory performance following napping in habitual and non-habitual nappers. SLEEP, 43(12), zsaa277, https://doi.org/10.1093/sleep/zsaa277.

 

Ong, J.L., Lau, T.Y., Lee, X.K., VanRijn, E. & Chee, M.L.W. (2020) A daytime nap restores hippocampal function and improves declarative learning. SLEEP, 43(9), zsaa058, http://doi.org/10.1093/sleep/zsaa058


Michael V. DeSanctis, PhD, Licensed Psychologist/Diplomate Board of Behavioral Sleep Medicine/National Register of Health Psychology Providers

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