Healthy napping

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This text is part of: "Science of sleep" by Piotr Wozniak (2017)

Napping is good

The natural sleep-wake cycle makes you feel less alert at mid-day. This period can easily be visualized using EEG measurements. In many tropical, subtropical, and Mediterranean countries this is the time for siesta. The drop in alertness can be magnified by a rich meal and a short nap is likely to quickly restore full alertness. However, the industrial nations do not seem ready to adopt the healthy habit of a postprandial nap. Just the opposite, when the Mexican parliament debated the law on statutory napping, politicians and comedians north of the border had a good laugh about "lazy Latin Americans". Siesta Awareness in the UK abruptly cancelled their National Siesta Day 2009 upon a publication from China that showed that diabetics nap more. Myths galore. Napping is smart, and yet nappers are often considered lazy, or weak. The self-improvement guru, Tony Robbins, provides a typical misguided get-up-and-go advice on napping: replace a nap urge with press-ups. Press ups will improve circulation and raise the level of catecholamines. This will make you feel more alert for a moment. However, only a nap can provide a true neural boost to your cognitive powers. Nap is better than exercise. Nap is better than caffeine. Nap is irreplaceable.

Napping and evolution

There are few theories on the evolutionary purpose of the mid-day dip in alertness. Most people believe that humans, as all other highly developed tropical animals, have developed a siesta habit as a way of getting around the midday heat. This explanation has also some cultural background as napping is by far less popular in moderate and cold climates. However, the alertness dip can be resolved by a short nap in minutes. This can make us active again long before the mid-day heat is over.

Another explanation is that the alertness dip is an atavistic remainder of the polyphasic sleeping mode that might have characterized human ancestors. Many animals and newborn babies sleep many times during the day. This might seem advantageous for optimizing memory circuits. However, consolidating sleep into a single night rest period might have offered some evolutionary advantage too. Early humans might have been less efficient in hunting and gathering activities at nighttime. This is why it might be advantageous to spend nights on memory optimization. Possibly, the consolidation of sleep went gradually from polyphasic sleep, through biphasic sleep to semi-monophasic sleep in modern humans. Actually, similar consolidation can be observed as we get older. By the time of adulthood we are more or less monophasic with a clear dip in alertness that may be resolved with a short nap. As we near retirement, we again seem to tend to become biphasic. This may be a result of the fact that working people are forced to suppress their biphasic tendency. We remain strongly biphasic throughout the lifetime, and the monophasic model has largely been imposed by industrialization.

When I look at learning performance data collected with SuperMemo, I see that the homeostatic decline in cognitive powers throughout the day is steep enough to provide an alternative explanation: nap is cognitively beneficial, but not essential enough to boost it with a full-swing circadian support. As a result, we have developed a half-way sleep system that ensures the essential fully blown nighttime sleep, and a window for an optional mid-day alertness booster. As the circadian component of sleep drive is associated with some physiological functions of sleep, a system with homeostatic napping might not have been equally beneficial. As for the speed of homeostatic decline in alertness, it could be inherent to the networks involved and might depend on energy reserves, supply of neurotransmitters, size of the networks involved, etc. It should also depend on the degree of use. The heavier the mental effort, the faster the decline in cognitive performance. In other words, for the brain as it is, and for heavy mental loads, slower homeostatic decline may simply not be physically possible. The timing of the mid-day nap comes from the fact that splitting the day into two exact halves maximizes overall alertness. Here again, mid-day tropical heat might actually provide an additional evolutionary incentive.

Naps and brain power

The father of the napping science, Dr. D. F. Dinges has spent many years investigating the problem of alertness at workplace and has shown substantial benefits of napping in professions where the alertness may be the difference between life and death. His research showed a substantial alertness boost coming from a nap (Dinges 1989[1]). He has also noticed relatively little impact of napping on the night-time sleep in regular nappers:

Sleep onset times among nappers an non-nappers (percentage)

However, when Dr Matthew Walker published his research proving the value of napping for cognition (Walker and Stickgold 2005[2]; Walker and Nishida 2007[3]), Dr. Derk-Jan Dijk commented surprisingly: "there was no clear evidence that daytime napping offered a distinct advantage over sleeping just once over 24 hours (...) while the brain effect reported in the study might be spotted in a laboratory setting, the picture became more clouded in the "real world"". Today, you can measure the benefits on napping on your own using SuperMemo. Comparing recall graphs of nappers and non-nappers, we can clearly see how non-nappers power at half-steam through the second half of their waking day (see: Biphasic nature of human sleep). Dr Walker, who confirmed his point with later research, says convincingly: "It's as though the e-mail inbox in your hippocampus is full, and, until you sleep and clear out all those fact e-mails, you're not going to receive any more mail". Take it from a religious napper Mr Winston Churchill: "you get two days in one"! The value of the nap increases in proportion to the degree in which your work depends on your brain and the quality of your thinking.

To nap or not to nap? Nap!

Here is a short summary of pros and cons of afternoon napping:

Pros:

  • Siesta naps, rich in NREM sleep, result in a significant increase in alertness that will be highly appreciated by people in creative professions. By various measures that boost may be as high as 50%!
  • As shown with SleepChart, napping improves recall and memory consolidation in the second half of the day
  • Well-timed napping may help combat sleep deprivation. Some people even prefer to sleep in two 3-4 hour portions throughout their lives!
  • Naps reduce blood pressure, improve cardiovascular health, and might, as a result, prolong your life!

Cons:

  • Badly timed (late) naps may worsen insomnia. This is why so many sleep experts counter-recommend naps. However, proper timing mitigates this problem
  • Badly timed (late) naps may result in sleep inertia. This can be resolved easily with proper nap timing.
  • Napping requires good rest conditions, conducive napping culture, and solid napping skills and habits. All these may be hard to come by in industrialized nations.

If you ever hesitate, to nap or not to nap, take a well-timed nap and see how it impacts your life. If you wake up groggy, remember that napping is also an art. Read about best timing of naps. Chances are, napping might become a beloved habit that will increase your productivity. Many great minds napped habitually. In addition to Churchill, notable nappers included Napoleon, Bill Clinton, and J. F. Kennedy. Interestingly, this group also includes a famous long-sleeper, Albert Einstein and a famous short-sleeper Thomas Edison. Even Bill Gates enjoyed taking naps under his desk in his creative programming years.

Napping in the corporate world

More and more companies in the US have already decided to make a switch from a coffee break to a napping break with special cubicles designed for nappers. In the future, this trend is likely to become more prominent as caffeine is not a fraction as effective as a nap in combating fatigue. For neural reasons, coffee, doughnuts, press-ups, and other methods taken together will never prove as efficient in mental restoration as a nap. At the same time, our society drifts strongly towards information processing where alertness is central to productivity. And when the productivity comes into the equation, corporations will definitely avail of the up-to-date research on napping.

Important! Do not confuse the healthy concept of a siesta nap with a very unhealthy idea of polyphasic sleep.

Napping rulebook

  • Do not use the alarm clock! Contrary to popular belief, well-scheduled nap will not result in sleep inertia (unless you are seriously sleep deprived). Alarm clock can seriously undermine the value of the nap!
  • Measure exactly the optimum length of the period between the natural awakening and the nap to maximize the effectiveness of a nap. The nap should come at the nadir of alertness, which usually comes 7-8 hours from natural waking. Napping beginners often miss the right timing! Choosing 7 hours as your starting point will allow of a 60 min. margin in case you were late for one reason or another. See: Best time for napping
  • Drink coffee or other caffeine drinks only after the nap. Even the tiniest amounts of caffeine in the system might interfere with the quality of sleep.
  • If you drink alcohol before the nap, it should be largely metabolized (i.e. out of your system) by the time you fall asleep
  • If you nap for more than 100 minutes, you probably need more sleep in the night (or you nap too late)
  • Avoid stress 1-2 hours before the nap. Even things you love can make you excited and make it harder to avail of the benefits of napping
  • Exercise is good. Try to finish your exercise at least 45 minutes before the nap. If you fail to cool down, your nap may end up prematurely
  • Meal before the nap is recommended. Unless your doctor says otherwise, your main meal of the day should actually come before the nap (around the 6th hour of your waking day)!
  • Sex before the nap is recommended
  • Stick to your ritual (e.g. stick to your best sequence: exercise, beer, bath, meal, quiet place, nap, music, or similar)
  • If the above advice does not work, you may need a month or so of trying. Mental slow-down is critical here! Many people do not discover the benefit of napping until some circumstances put them into the routine (e.g. heart condition diagnosis). Even if you cannot fall asleep, you may still need a nap! Sleeplessness may only be a result of a habit or your inability to forget the worries of the day. You may simply not fully understand your actual sleep needs.
  • If it all won't make you fall asleep in 10 minutes even after a month of trying, you can probably safely give up napping for good
  • When sleep deprived you may need 20 minutes of naptime per one hour of sleep lost (see: Power nap)

References

  1. Dinges D.F. and Broughton R.J., "Sleep and Alertness: Chronobiological, Behavioral, and Medical Aspects of Napping," (New York: Raven Press, 1989), 171-204
  2. Walker M.P., PhD and Stickgold R., PhD, "It’s Practice, with Sleep, that Makes Perfect: Implications of Sleep-Dependent Learning and Plasticity for Skill Performance," Clinics in Sports Medicine / Volume 24 / Issue 2 (April 2005): 301-317, doi: 10.1016/j.csm.2004.11.002
  3. Nishida M. and Walker M.P., "Daytime Naps, Motor Memory Consolidation and Regionally Specific Sleep Spindles," PLoS ONE / Volume 2 / Issue 4 (2007): e341, doi: 10.1371/journal.pone.0000341