Power nap

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

Power of a nap

The art of napping has the power to double creative productivity. Churchill was a famous biphasic sleeper. His naps let him squeeze two productive days into 24 hours. The explanation lays in the natural creativity cycle. However, those who try to emulate Churchill or Edison often fail to follow the facts of science and fall into a trap of sleep mythology. The most notorious blunder committed by young adepts of better sleep is the confusion between biphasic sleep and polyphasic sleep.

For a nap to express its full power, the following conditions must be met (in order of importance):

  • it should take place at the center of the midday circadian nadir (see: Best nap timing). This corresponds with Mediterranean siesta
  • it cannot be regulated with alarm clocks, caffeine, or other sleep "tricks". Coffee naps are a good idea for people in a hurry, not for those who care about brain productivity
  • it should be the only nap of the day (i.e. it cannot be part of a polyphasic sleep schedule)
  • it works best in free running sleep with no sleep deficit
  • it works best in people with no physical or mental health issues
  • it works best in habitual nappers who improved the quality of their naps from month to month by adjusting and perfecting little details in their surroundings. Beginners are often too anxious to fall asleep

Compensatory nap

There is a correlation between the duration of a nap and the duration of the night sleep. The relationship between the two is non-linear:

Correlation between the duration of nighttime core sleep and the total duration of naps

In the presented example, a negatively exponential function provides a good fit to data. However, in the most studied range corresponding with the nighttime sleep ranging from 4 to 8 hours, a nearly linear relationship can be observed where each hour of lost night sleep requires 20 min. of replacement nap time. This shows that napping has a powerful compensatory power.

One midday nap should be all that's needed to compensate for lost night sleep. As a result, it makes more sense to replace a number of naps with a single nap whose duration will depend on the amount of lost sleep:

NapDuration = (SleepRequired - SleepObtained) / 3

This formula will hold only for properly timed naps. Early naps will not provide full compensation. Late naps will last longer and will shorten sleep in the following night.

Night time sleep deficit requires extra napping time in 3:1 ratio. For each hour of lost night sleep, extra 20 minutes of napping is needed

This formula should only have a theoretical value. You should never try to terminate a replacement nap. If it is properly timed, it should be allowed to run its natural course and it will then provide the best compensation for sleep lost in the night.

Even though naps provide an excellent compensation for lost sleep in the night, they cannot provide a full functional replacement. To achieve your maximum cognitive capacity, you need to run your night sleep uninterrupted until completion!

Sleep debt and napping

PureDoxyk is the nick of the "inventor" of the "Uberman sleep schedule". Even though she claims to have slept polyphasically for a longer while, a more detailed look at her reports indicates that she slept in a sort of messy multi-nap compensatory sleep system that gradually gravitated in the direction of a pretty natural biphasic sleep that she later termed "Everyman sleep schedule". Were it not for that gravitation and a tendency to take a "core sleep", I might even suspect that the inventor of the Uberman sleep cycle suffered from a rare mutation that causes circadian arrhythmicity. People with that disorder cannot sleep well in a long block over the night and take multiple naps during the day. Those naps add up to a pretty normal total sleep duration and produce a pretty unrefreshed mind that makes the disorder pretty hard to live with. It would be an ironically sad turn of events if a sick person suffering from bad sleep could have proposed a sleeping "system" that caused an epidemic of lifestyle experimentations by teenagers looking for better sleep only to find more sleep-time misery.

PureDoxyk Law

What strikes me in PureDoxyk writings is that she instantly rings credible and seems to have a very good sense of the link between sleep deprivation and napping. Let's have a peek at her claim that I will call PureDoxyk Law. Note the "six hour sleep" fragment that indicates that PureDoxyk is not suffering from a serious circadian arrhythmicity disorder as speculated above:

Six naps no sleep; 4 naps one-point-five hours sleep; 3 naps three hours sleep; 2 naps four-point-five hours sleep; one nap six hours sleep*.

Note (*): I removed two tiny mathematical kinks from the law which was originally formulated as: Six naps no sleep; 4-5 naps one-point-five hours sleep; 3 naps three hours sleep; 1-2 naps four-point-five hours sleep; one nap six hours sleep (source)

Obviously, this law would need to be parametrized to fit a general healthy population. In particular, most monophasic sleepers will find it hard to nap more than once per day unless all sleep episodes in question are terminated with an alarm clock, perpetuating the cycle of sleep deprivation.

We can instantly see a nearly perfect linear nature of the relationship between the duration of the night sleep and the number of naps taken.

NapNumber = 5.6 - 0.8*CoreSleep

PureDoxyk law in biphasic sleep

If we take the formula for the number of compensatory naps taken by PureDoxyk and apply it to biphasic sleep we instantly see that in a natural healthy biphasic sleep cycle with a single siesta, PureDoxyk law yields a night-time sleep of 5.75 hours.

This number is eerily similar to my own night-time average. Out of sheer curiosity I checked my average nighttime sleep for the years 2000-2017 and was pretty shocked to see it is was 5.69 hours. This might be just a coincidence, but the irony of that coincidence is staggering. I have been critical of polyphasic sleep mythology since 2002 or so, and it appears my sleep needs are almost identical as those of the only "natural" polyphasic sleeper in existence!?

Sleep and aging

While checking on my night sleep average, I also noticed that my night sleep kept getting shorter over decades. The graph is actually pretty scary. If the trend continues, I will soon enter night-time sleeplessness and die like rats in Rechtschaffen experiments.

Night sleep over 18 years collected with SleepChart

Figure: Average length of night time sleep decreasing in the course of two decades (Wozniak 2000-2017)

It is true that with aging our sleep needs might diminish slightly, esp. if our brainwork slows down or health deteriorates. However, I am glad to know that with compensatory napping at 1:3 ratio, my value sleep total might have actually increased (NightSleep + NapSleep*3). The optimistic interpretation might be that in free running sleep, with improvements in the art of napping, the demand for night sleep might drop. Perhaps Dr Kripke would be glad to see a case of improved sleep quality with less sleep. For more see: Biphasic life

Summary: Napping

  • good siesta can double creative productivity (see: Natural creativity cycle)
  • siesta should be taken 7-8 hours from natural waking (see: Best nap timing)
  • alarm clock undermines the value of napping
  • caffeine before the nap undermines the value of napping
  • caffeine after the nap may boost the effect of napping
  • one nap per day is optimum (see: Healthy napping)
  • habitual nappers improve nap quality over years of the habit
  • nap compensate slow-wave sleep needs in roughly 1:3 duration ratio
  • short night sleep may be a sign of bad health, aging, or a sign of good sleep (see: How long should we sleep?)