It is not a secret that sleep is important for overall health, especially for the proper brain functioning and successful performance of daily tasks. Lack of sleep during the night forces many of us to take a daytime nap. Is this a good practice? Scientific research shows that a short daytime nap can be a good idea even if you don’t suffer from sleep deprivation at night.

The importance of sleep is evident starting from the early childhood, as the baby’s sleep pattern influences his/her cognitive development. More importantly, how we sleep as babies has an impact on our productivity later in life. Short night sleep duration in toddlers has been linked to their poor cognitive performance as they enter the school. One study demonstrated the relationship between vocabulary (i.e., language development) and sleep pattern in infants and toddlers, with particular importance of daytime naps. It turns out that daytime nap has the same importance as night sleep, if not even bigger.

Apart from reducing sleepiness, mid-day naps offer benefits such as memory consolidation, better learning, better tasks performance, as well as improved emotional processing. Unfortunately, the habit of staying awake for most of the day has become a widespread phenomenon, especially in the developed, industrialized countries where the constant drive for all day work and profits is overwhelming. However, researchers are convinced that we are physiologically prone to snooze during the so-called nap zone between 2 and 4 pm since our brain seems to prefer to toggle between wake and sleep more than once a day.  So, during one of those days filled with multiple work tasks, we probably should take a break and rethink how siesta can benefit us.

Studies have indicated that naps can sharpen our brain, i.e., improve concentration in both fully rested and sleep-deprived individuals. This can lead to significantly better performance of various tasks, from driving to all kind of work assignments. One interesting study retrospectively analyzed the incidence of highway car accidents occurring to shift-working police drivers. What this study confirmed is that napping before night shift effectively improved performance and reduced number of car accidents by almost 50%.

Another trial investigated the effects of 40 minutes nap at 3 am on cognitive and psychomotor performances in nurses and physicians working 12-hour night shifts at an emergency department. The researchers tested attention and memory scores of these workers at three points in time: before, during, and after the night shift. The workers were split into two groups: one group had a nap, and another group worked continuously without napping. The result was quite revealing: workers that had a nap scored better at attention tests after the night shift and performed work assignments (such as inserting a catheter) more successfully than the non-napping group.

Some researchers suggest that even brief naps can improve cognitive performances. One trial investigated benefits of the naps of different duration compared to no naps at 3 pm after nocturnal sleep restricted to 5 hours only. While five minutes naps provided no benefits, when compared with no nap, 10, 20 and 30-minutes naps resulted in improvements of measured outcomes, including cognitive performance. Overall, 10 minutes naps were identified as the most efficient, as they provided almost immediate improvements lasting for more than 2 hours.

So, what happens in the brain during those evidently beneficial naps? Regardless of the time, we spend sleeping during the night, sleepiness increases during the day and leads to the decline in cognitive abilities, including working memory. Mid-day naps (siesta) can reduce this decline by minimizing the homeostatic sleep pressure. Homeostatic sleep pressure results from the accumulation of adenosine, a by-product of cellular metabolism. Adenosine is recognized as an important sleep factor, and its accumulation is amplified with more time spent awake. Naps improve executive functions by reducing sleepiness (i.e., improving alertness) via this mechanism involving adenosine. Besides, there is a possible alternative mechanism that involves the interaction of adenosine and dopamine regulating pathways in the brain parts crucial for executive functioning.

Naps enhance memory integration, i.e., solidification of previously learned information and improvement of subsequent learning. This is assumed to be mediated by activation of brain cells in the hippocampus, an important brain part associated mainly with memory and learning. Activation of the hippocampus during the learning in the sleep-deprived brain is altered. It has been proposed that this alteration mediates the association between sleep loss and learning deficits.

Research findings also suggest that there is a bidirectional link between sleep and emotions, and poor sleep is often associated with poor mental health. Thus, by improving sleep patterns, naps could be an efficient tool for emotional regulation. Research on children has shown that napping promotes more appropriate and mature responses to differing stimuli. Children taking naps respond more positively to positive stimuli, and less negative to negative/neutral stimuli compared with children deprived of napping.

To sum it up, there is a growing body of evidence that daytime nap is not just a decadent luxury. It helps to improve brain performance in people of all ages and regardless of how well they slept at night. It improves memory, enhances alertness, improves performance and learning. These facts confirm the wisdom of having a siesta, as the benefits of such practice compensate for the time lost during the busy working part of the day.

References

Horváth, K., Plunkett, K. (2016). Frequent daytime naps predict vocabulary growth in early childhood. Journal of child psychology and psychiatry, and allied disciplines. 57(9): 1008-1017. DOI:  10.1111/jcpp.12583

Garbarino, S., Mascialino, B., Penco, M.A., Squarcia, S., De Carli, F., Nobili, L., et al. (2004). Professional shift-work drivers who adopt prophylactic naps can reduce the risk of car accidents during night work. Sleep. 27(7): 1295-1302. PMID: 15586782

Smith-Coggins, R., Howard, S.K., Mac, D.T., Wang, C., Kwan, S., Rosekind, M.R., et al. (2006). Improving alertness and performance in emergency department physicians and nurses: the use of planned naps. Annals of Emergency Medicine. 48(5): 596-604. DOI: 10.1016/j.annemergmed.2006.02.005

Brooks, A., Lack, L. (2006). A brief afternoon nap following nocturnal sleep restriction: which nap duration is most recuperative? Sleep. 29(6): 831-840. PMID: 16796222

Mantua, J., Spencer, R.M.C. (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

Berger, R.H., Miller, A.L., Seifer, R., Cares, S.R., LeBourgeois, M.K. (2012). Acute sleep restriction effects on emotion responses in 30- to 36-month-old children. Journal of Sleep Research. 21(3): 235-46. DOI: 10.1111/j.1365-2869.2011.00962.x

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