Optimizing the timing of brainwork

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

Optimizing the timing of brainwork

Twice each day, we peak in intellectual performance. We can improve our productivity by understanding the circadian cycle

Circadian graph and brainwork

Charting the circadian cycle makes it possible to find best windows of time for brainwork. The following exemplary circadian graph was generated with SleepChart using a log of free running sleep:

Optimizing the timing of brainwork with respect to the circadian cycle.

Figure: Optimizing the timing of brainwork with respect to the circadian cycle. This exemplary graph was generated with the help of Sleep Chart on the basis of 3-year-long daily measurements of a free-running sleep rhythm. The horizontal axis expresses the number of hours from awakening (note that the free running rhythm period is often longer than 24 hours). Light blue dots are actual sleep episode measurements with timing on the horizontal, and the length on the left vertical axis. Homeostatic sleepiness can roughly be expressed as the ability to initiate sleep. Percent of the initiated sleep episodes is painted as a thick blue line (right-side calibrations of the vertical axis). Adenosine-related homeostatic sleep propensity increases in proportion to mental effort and can be partially cleared by caffeine, stress, etc. Circadian sleepiness can roughly be expressed as the ability to maintain sleep. Average length of initiated sleep episodes is painted as a thick red line (left-side calibrations of the vertical axis). Mid-day slump in alertness is also circadian, but is biologically different and results in short sleep that does not register as red sleep maintenance peak. Sleep maintenance circadian component correlates (1) negatively with temperature, ACTH, cortisol, catecholamines, and (2) positively with: melatonin and REM sleep propensity. Optimum timing of brainwork requires both low homeostatic and circadian sleepiness. There are two quality alertness blocks during the day: first after the awakening and second after the siesta. Both are marked yellow in the graph. For best learning and best creative results use these yellow blocks. Caffeine can only be used to enhance alertness early in this optimum window (brown). Later use will affect sleep (caffeine half-life is about six hours). Optimum timing of exercise is not marked as it may vary depending on the optimum timing of zeitgebers (e.g. early morning for DSPS people and evening for ASPS people). For more details see: Circadian graph and Biphasic nature of human sleep

Best brainwork time

Optimum timing of brainwork requires both low homeostatic sleepiness and low circadian sleepiness. There are two quality alertness blocks during the day: first after the awakening and second after the siesta period. Both are marked as yellow blocks in the graph (above). For best learning and best creative results use these yellow blocks for brainwork. Caffeine can only be used to enhance alertness early in this optimum window. Later use will affect sleep (caffeine half-life is about six hours). Optimum timing of exercise may vary depending on your exercise goals and the optimum timing of zeitgebers (e.g. early morning for DSPS people and evening for ASPS people). In this example, the stress block is followed by the exercise block to counterbalance the hormonal and neural effects of stress before the siesta. Unmarked white areas can be used for the lunch (before siesta) and fun time unrelated to work in the evening at a time when the ascending circadian sleepiness makes creative work ineffective. That white evening protective zone should be free from stress, alcohol, caffeine, etc. Recommended activities might include fun, games, relaxation, TV, reading, family, DIY, housework, etc. For inveterate workaholics, less challenging and stress-free jobs might also work ok. The best litmus test for a well designed day is that all activities should be fun! Brainwork is fun only if your brain is ready. Sleep is fun if you are ready. Rest and entertainment feel in place only after a productive day. Even a bit of stress can be fun if it is properly dosed and timed. You do not need to be an adrenaline junkie to enjoy your stress and exercise slots. There is little exaggeration in saying that a good understanding of the circadian cycle is the key to a happy and productive day!

For more see: Natural creativity cycle

Balanced 24 hour cycle

The slanting green line separates the graph into the areas of phase advanced (right) and phase delays (left). The line is determined by points in the graph where the waking time (horizontal axis) added to the sleep time (left vertical axis) equals to 24.0 hours. The place where the green breakeven line crosses the red sleep length line determines the optimum balanced sleep cycle of 24 hours. In the presented example, 17.35 hours of waking, added to the expected 6.65 hours of sleep time complete a balanced full 24 hours sleep-wake cycle. The greater the angle between the green and red lines, the harder it is to balance sleep and fit it into the 24h cycle of the rotating earth. In the example, adding waking hours does not shorten sleep much enough to make the balance easy. This implies that a religious adherence to a 17.35 day may be necessary to balance the cycle. However, this shortened waking day may increase sleep latency and increase the probability of premature awakening, which can also tip the balance towards the phase delay. The vertical aqua line shows where the expected sleep time added to the waking time equals to 24 hours (crossover with the green line representing a perfect 24-hour day). In DSPS or ASPS that 24h balance may be hard to accomplish. For example, without medical intervention, only a large protective zone in the evening, early nap (or no nap), and intense morning exercise can help balance the day in DSPS.

Important! This graph is based on data that is true solely for a free running sleep condition. If you use an alarm clock to regulate the timing of your sleep, this measurements and recommendations may not apply! In addition, timing and the amplitude of changes differ vastly between individuals!

Sleeping against your natural rhythm

If you sleep against your natural rhythm you will often experience tiredness or drowsiness that can be resolved by adjusting the sleeping hours. In healthy individuals, the daytime alertness is primarily determined by:

  1. circadian phase and homeostatic sleepiness
  2. total sleep time the night before
  3. amount of slow-wave sleep the night before
  4. regular adherence to the sleep-wake schedule in preceding days
  5. sleep deficits accumulated in the preceding days (e.g. REM deficit, SWA deficit, etc.)

All those factors are closely associated with the sleep phase. Free running sleep provides the best way to maximize the alertness throughout a waking day. Free running sleep is likely to shift the minimum temperature point from the early morning closer towards the middle of the subjective night. You should notice increased sleepiness before going to sleep and no sleep inertia upon awakening! If you cannot free-run your sleep, it is very important to understand the relationship between your homeostatic and circadian sleep drives as compiled in the table below. In the course of the day, you should move in sync between the yellow areas of the table, i.e. from perfect alertness to maximum sleepiness, and then back to perfect alertness. The gray areas illustrate when your sleep falls out of sync:

High circadian sleepiness Low circadian sleepiness
High homeostatic sleepiness Peak of the night: You are very drowsy and fall into refreshing sleep with latency of less than five minutes Insomnia: You are tossing and turning in bed. You are very tired but you cannot fall asleep. Your temperature, blood pressure and pulse are raised. Your thoughts are racing

Solution: Wait for the arrival of the circadian phase. Delay going to sleep by 3-6 hours

Low homeostatic sleepiness Hypersomnia: You are drowsy throughout the day despite long sleep hours. Napping does not help. You show minimum energy levels. Your muscles are weak and atonic

Solution: Adjust your sleep phase to your circadian (e.g. try to go to sleep 3-6 hours later)

Peak of the day: You are alert, energetic, and full of new ideas

Kill the alarm clock!

Alarm clock epidemic

Few upwardly mobile people in the modern rat-race society can live without an alarm clock. With a shot of strong coffee and round-the-clock stress, most people learn to live and survive with an alarm clock. Half of the population wakes up with an alarm, 9% are woken by a partner, 4% by pets, 3% by children, etc. That leaves a minority that wake up naturally. Increasingly, time becomes the most precious commodity in society where achievement is often associated with speed and perfect time-management. However, alarm clocks introduce harmful side effects: stress, sleep debt, and worst of all, disruption of the natural physiological sleep function. At worst, those factors will result in physical damage to the brain (e.g. such sensitive structures as the hippocampus, your memory switchboard, may literally lose neurons as a result of disrupted sleep).

The art of time-management makes it possible to live at a high speed with an alarm clock at your side, and still be free from stress. However, the societal damage inflicted by alarm clocks and sleep deprivation is unforgivable. An alarm clock that interrupts your sleep damages your memories, your ability to learn, your creativity, your mood and temper, your relationships with other people, your ability to focus, and your overall intellectual performance!

Dr Robert Stickgold has shown that people who learn a skill during the day do not show significant improvement until they get 7-8 hours of good sleep[1]. There was a noticeable correlation between the degree of improvement and the quality of sleep received. My own work with SleepChart also shows that the use of alarm clocks can dramatically reduce memory recall and consolidation. Forgetting is so painless that we rarely notice its effects. In a natural way, forgetting will proceed even if you get as much sleep as you need, and it is difficult to point to specific memories lost as a result of not sleeping enough. Moreover, sleep deprivation may leave your memories intact while their storage will be sub-optimum. The difference may be impossible to spot without measurement. We are more likely to notice sleepiness, reduced mental agility, or bad mood.

Disrespect for sleep has reached biblical proportions. This is most noticeable in the US and other highly industrialized nations. Men's Health's Dan Vergano writing for ABC News in "No More Rude Awakenings" suggests a seven-day system for fighting sleepiness: "The secret is to fuel that arousal system so it can beat the pants off the sleep system. By creating the kind of feel-good expectations that trigger hormones to wake the brain, you’ll override the need to sleep and be able to jump out of bed like a man on fire". The article suggests a "fresh" mind method that capitalizes on the fact that stress hormones help keep you alert. However, the only rational remedy for "rude awakenings" is simple: get enough sleep! Jumping like a man on fire is not likely to have a positive effect on your creative potential!

You may often notice that waking up with an alarm clock gives you a jumpstart for the day. You may then come to believe that using the alarm clock might help you stay alert later in the day. This is not the case. The alarm signal simply scares your brain into wakefulness, disrupting the carefully planned process of neural optimization that occurs in sleep. As a result, you get an immediate injection of adrenaline and your levels of ACTH and cortisol also increase. This is cortisol that peaks at awakening in natural sleeping rhythm that provides you with the fresh-mind impression. With passing time, this cheaply gained alertness will wear thin unless you continue abusing your physiology with more "remedies". You may use more scare tactics for keeping yourself alert, abuse caffeine, or even get a more profound effect with modafinil, cocaine, or amphetamines. Alertness should be achieved with the help of sufficient sleep, not despite the lack of sleep! Apart from your reduced ability to learn new things, all unnatural anti-drowsiness methods will produce a great deal of side effects that can be pretty damaging to your health in the long run.

All efforts to overcome sleepiness by means other than sleep itself can be likened to a chase of the first high in the use of psychoactive substances. If you drink buckets of coffee, do pushups, pour cold water over your head, or slap your face, you only dip into the last reserves of your alertness hormones that only worsen the effects of deprivation after the effects of the stimulation wear off, which is usually a matter of minutes. Rarely can you get a boost lasting more than an hour, and the more you perk up, the lower you fall in the aftermath.

Insomnia trap

If your life without an alarm clock may seem like an impossibility, you will probably need to use all methods in the book to be sure you get enough sleep and minimize the damage. If you need to wake up early at the cost of your brain, avoid the insomnia trap! Insomnia trap is a vicious circle of:

  1. going to sleep too early to get more sleep,
  2. failing to fall asleep in time (or worse, waking up prematurely),
  3. feeling even more tired on the next day, and
  4. going to sleep even earlier on the next day to catch up with the lost sleep.

It is better to go to sleep at a natural hour (i.e. a bit later), wake up early, suffer a degree of sleep deprivation, and hope for a phase reset that will make it possible to continue on the designer schedule. For a solution to the insomnia trap see Curing DSPS and insomnia.

If you cannot reset your phase and still feel tired when getting up early on a regular basis, consider choosing a job that is acceptable for your body, not the other way around. Your long-term health and well-being is at stake. If you absolutely cannot live without an alarm clock, you can at least start from changing your mindset about the importance of sleep and ensure you do not impose wrong habits on your children. Perhaps the young ones will be lucky enough to work in a flex-time system that will make it possible to get sufficient amount of undisturbed sleep. At least, do not set a bad example!

Wake up the President

President Bill Clinton was woken up twice by telephone during the night of April 22, 2000 before the infamous I.N.S. raid on the home of Miami relatives of the young Cuban exile Elian Gonzales. He was probably the most often disrupted and sleep deprived president in history. Only after a heart surgery did Clinton take diet, sleep and (real) exercise seriously. Those interrupted nights would definitely influence his performance and the quality of his decisions! Has anybody thought of a rule: Do not wake up the president? A rule that could only be revoked in a true national emergency? President G. W. Bush (b. 1946) was woken up when an American spy plane landed in China in 2001. He was also woken up after a suicide bombing in Jerusalem in 2002. George H. W. Bush (b. 1924) and Hilary Clinton made "waking up in the middle of the night" part of their presidential campaign and prowess. It seems that only Ronald Reagan had pretty strong rules for protecting his own sleep. He also famously napped during some cabinet meetings. He slept through a couple of international events without an apparent negative impact on his somewhat delayed decision-making. Critics would say he slept through the entire Iran-Contra affair. Was Reagan so protective of sleep because he understood the role of sleep better, or perhaps he was just a bit lazier than other presidents? I don't know. However, he sure set a good example.

Alarm clock monsters

Andrea K. wrote to me with skepticism: "Take the alarm clock away from a typical person and they won't just wake up on their own at their desired time and they will miss work, school, or whatever. An alarm clock can't be that bad for you because of the simple fact that most people use it and I never noticed any problem with them :) Everyone in my family has been using one since they were children, and no one suddenly went crazy or began to mutate into a monster (yet)!" As I wrote earlier, when you use an alarm early in the morning in order to get to work or to school, you cut off the later stages of sleep. If the intrusion into natural sleep is not large (e.g. from minutes to an hour), the damage may be limited. Alarm clock will do far more damage if it cuts deep into the middle of the night sleep. You can compare the use of alarm clocks to smoking or eating hot dogs. The harm is not great enough to be instantly noticeable. It took the public many years to largely accept that "smoking is bad" or "fast food is bad". It is hard to quantify the degree of damage. However, as we move to knowledge society where our intellectual performance becomes increasingly important, the effects of sleep deprivation will come under closer scrutiny and alarm clocks are bound to gradually fall out of favor. Unlike hot dogs, they are already universally hated by their users. Most people are able to somewhat adapt their sleep to their schedules if their routines are regular enough. When those people need to resort to the use of the alarm clock, they cut less of their sleep and the damage is proportionally smaller. Nevertheless, we should always strive at eliminating alarm clocks altogether. Most of all, we should protect our kids from suffering interrupted sleep!


  1. Stickgold R., "Sleep-dependent memory consolidation," Nature / Volume 437 (October 27, 2005): 1272-1278