Factors that affect sleep

From supermemo.guru
Jump to: navigation, search

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

Stress

Stress is a sleep killer. Hormones associated with stress, such as adrenaline, ACTH, cortisol, etc. increase alertness and reduce the sleep propensity. It is more difficult to initiate sleep in conditions of stress. Nighttime awakenings are more likely. The sleep structure may also change. The sleep may become shorter and less refreshing. Moreover, sleep deprivation will magnify the effects of stressful situations. Stress and bad sleep conspire hand in hand to make life miserable for quite a number of people in industrialized nations. Those who are sleepy and in stress are less likely to achieve their goals. That only adds to the misery.

In addition to its effects on sleep, stress may have a negative influence on creative work, learning, problem solving, etc. At its worse, stress can virtually shrivel your brain! Persistent stress and raised corticosterone levels have been shown to decrease BDNF in rat brains. This leads to the atrophy of the hippocampus - the chief memory switchboard! Stress can cut down your IQ. Not only for a day, but also, to a lesser degree, for a lifetime!

Stress is rooted in our emotional brain. Emotions are very difficult to control and will often determine a person's chances for success or failure. Negative emotions, such as anger, are counterproductive and contribute little to a person's growth. Positive emotions, such as well-dosed passion, help one overcome obstacles that are bound to be found on any race-course. Emotions are also transitive and tend to amplify in social groups. Anger begets anger. Cordiality begets cordiality. Your effort to beget positive emotions, in suitable circumstances, will send positive ripples through the social circles you interact with. Learn to capitalize on positive emotions and circumvent negative emotions. Invite all positive emotions that help you execute your grand plans. Condition yourself to love your work, people, and the world. Run away from sources of negative emotion.

The power of emotion comes from the fact that they are wired into the low-level brain structures that cannot easily be controlled by rational thinking governed by the prefrontal cortex. An angry individual can command its brain to cool down, however, he cannot instantly reduce the level of adrenaline that has already been released into the bloodstream. A drug addict can rationally decide to give up drugs, but when the physical effects of the craving hit his system his rational brain is often powerless.

As it is hard to combat one's reactions to stress, one of the best ways to deal with stress is to run away from it. Stress is so important to your well-being that, if possible, a change of a job, a change of friends, a change of residence, or a change of lifestyle must be considered! Without these, even the best counter-stress advice may not work. Some people are inherently prone to stress and may find it impossible to live a life without it. Others may thrive on stress (to a degree). This article cannot possibly even touch the tip of this troublesome iceberg. If you suffer from bad sleep and stress, tackling stress may be your top priority thing to do. There are tons of books and blogs that deal with the issues of stress. It may seem redundant to produce yet another list. However, I thought I would make a selection sorted by how much I believe it could be helpful, esp. with the view to sleep and creative work. I believe that prioritization by informative power as opposed to the curative power is important. For example, good health might be the most important factor in combating stress, however, you are probably already working hard on it. On the other hand, fewer people realize the effectiveness of pain in curing one's troubles! I am no expert in stress management, and I have been blessed with pretty strong stress tolerance that can make it hard for me to come up with a comprehensive list. If you think I could add something worth recommending to others, please let me know. Here is my list:

  • exercise: if you impose a pain of exercise, your other pains may be seen from a new perspective. Try marathon or winter swimming. Few things can bring as much relief and pleasure as pain! Exercise helps you grow the brain - your best anti-stress ally. On the other hand, sleep deprivation and stress shrivel the brain making it harder to struggle through life.
  • eliminate interruption: wherever possible, create protected zones in your day when you can focus on creative work. If possible, your entire morning should be protected to keep your mind clear. In that period, e-mail, phone calls, and meetings are all forbidden. If the protected zone follows a period of stress, you may never get back to your best mental shape. Take occasional creative vacations when nobody can reach you. If this is too much, try it once. Perhaps you will see your entire life in a new context.
  • measure the day: instead of measuring your distance to the goal, measure how much you have accomplished on a given day. If your goals are ambitious enough, most of the time they will be pretty remote far on the horizon. With your eyes on the horizon, you do not have a good sense of progress. If you focus on the jobs for the day, you will get a better sense of the positive motion. Do not wait for the great trophy. Let the little good deed be its own reward. Once you reach a higher level of satisfaction with little things, your brain may work on a higher gear and perhaps carry you beyond your original target.
  • simplify: simple living is more fun. Simplicity is a great escape from the rat race. Some ideas: ride a bike instead of driving a car, give up some of electronic must-have gizmos, try to live without deadlines, make fewer promises (including yourself), turn off your cell phone, take a creative vacation (one job, one goal, no distractions), etc. If you work on too many projects, try to finish one before you begin another. Learn to say "no" or avoid situations in which you have to say "no". Learn to delegate. If you are overloaded with information or e-mail, dump it all to SuperMemo and prioritize.
  • creative work: I believe that few things are as fulfilling as creative work for a good cause. If you can sacrifice lesser things for a major creative goal, do it each time you have a chance. In the long run, productivity of the mind is one of the best formulas for a happy and healthy living.
  • slow down: if you always keep running out of time for doing things, you might be loading too much on your plate. This magnifies your stress levels, and gives you an excuse to delay sleep. It is good to be fast and efficient, however, this cannot stretch beyond a certain biological limit where you shortchange your life for today's minor accomplishments.
  • prioritize: one of great ways to pile up stress in the long-run is to procrastinate or work on fun things while neglecting the rest. You need to always prioritize honestly and religiously execute by priority. There will always be a long bottom of the list that will need to be ignored. Ignoring the overload and focusing on top-priority jobs is a thing everyone needs to learn. One of the ways to prioritize effectively is to use tasklist sorted by priority = value/time. Dumping tasks on a tasklist is both stressless (you always hope to execute at some point) and efficient (you always work from the top of the list).
  • sleep: even though we speak of sleep as a goal, sleep is also great for clearing up stress. However, this weapon is effective only if you can run your sleep free. This is due to the fact that stress itself may cause phase delays. This means that you may need to delay sleep slightly and get up a bit later. If you need to get up early, sleep is less likely to be your ally. If you get into an unsettling situation that spoils the day, you can always hope for some solid exercise followed by some solid sleep. Hang on to the comfortable thought that human biology will work for you. Stressful situations often seem much more stressful when stress adds up. Stress multiplies stress. Good sleep gives you a new, more honest perspective on today's worries.
  • be nice: if you have something positive to say to someone, say it! Help others go through the day with a smile. If you have something negative on your mind, ponder if expressing it is necessary. Small things are not worth fighting for. When you are in a bad mood, remember than even if you force onto yourself a bit of niceness for others, you will see that niceness is infectious, you will get some back and a day will feel sunnier. If this advice does not work, perhaps you are in a wrong environment?
  • family: family is a chief source of stress for many. However, it can also be the best form of stress relief. If you are just about to build a family unit, keep in mind that stress-free life in a long-term should be one of your chief goals. If your relationship is a string of worries with no light in the tunnel, perhaps it is not your best long-term investment?
  • nature: sadly, many of us lost the ability to feed on the beauty of the natural world. For a stressed workaholic, a trip to the woods or the mountains feels like a waste of time that only magnifies the stress. However, the love of nature is atavistically dormant in everyone. It can be reawakened. It can be re-learned. Once it is restored, contact with the nature is one of the best stress relievers. Needless to say, nature preserves should be mobile phone free zones!
  • contentment: one of the best ways to boost one's resistance to stress is work on one's overall contentment. Research shows that contentment is primarily based on self-esteem, relatedness (relationships with other people), autonomy (being in control) and competence (being productive). To a degree, all these factors can be influenced. Contentment makes it easier to ignore minor annoyances and see the big picture and big goals.
  • avoid conflict: go to battle only for major life-changing causes. Too much time on this planet is spent on battling for or against little things and/or minor principles. A great deal of conflict can be resolved by just ignoring it and focusing on more important things.
  • avoid bad people: one of the chief sources of stress is other people. Some of them are good people that bring stress by virtue of their job, duty, good intent, ignorance, etc. Others are just plain bad people that would best be avoided. In your choices of a spouse, job, gym, friends, etc. make sure you stay away from people with a talent for spoiling your day. Those choices will determine your stress levels, your ability to sleep and your ability to focus on things that are important.
  • plan ahead: when you wake up with a set goal for the day, your mind is taken away from stressful distractions and your productivity soars. Review your goal lists regularly to refocus the mind. You need separate goals for work, family, exercise, etc. They are all helpful in a smooth and productive sail through each and every day.
  • time-management: solid time-management is essential for productivity. Low productivity begets low productivity. Once your efficiency drops, it will have a negative impact on your motivation undermining your progress even further. In terms of a nagging stress, few things are as bad as piling lists of things undone. Those nagging lists are best tackled with time-management (getting things done), and prioritization (getting rid of things than cannot be done). Consider Plan in SuperMemo for time-management, and Tasklists in SuperMemo to stresslessly cut the bottom of the to-do list.
  • health: healthy lifestyle is vital. Healthy body makes stress management easier. Here sleep can be a part of a negative feedback loop (less sleep, more stress, less sleep), or a positive feedback loop (good sleep helps combat stress, stress management helps you sleep better, etc.)

For more, see this immortal text: The Medical Basis of Stress, Depression, Anxiety and Drug Use!

Eustress

A degree of stress can also be a positive force. Some forms of stress are great energizers. I believe that when optimizing one's day for good sleep, good learning, and good creativity, it makes good sense to take into account the timing of stress. Stress before sleep will have a negative impact on sleep. Stress before creative work or learning will have a negative impact on the results of brainwork. A vast majority of people do not have much influence on the timing of stress. Stress seems to pervade all our lives. However, if you belong to the lucky few who can decide when to open a letter, read mail, make a difficult call, schedule a tough meeting, tackle a stressful task, you should try to employ stress to work to your advantage. I believe that the best and the only right time for tackling stressful situations is before or at siesta time. This timing spares the most creative morning period, and provides a sufficient time buffer before the night sleep. Moreover, it helps you sail through the less productive section of the day, including the mid-day dip in alertness (if you cannot afford napping). If you are a napper, adding exercise after the stress slot could pretty efficiently flush away the effects of stress. A dose of stress can actually improve the efficiency of exercise, and if exercise is not efficient enough to erase the effects of stress, you will be sacrificing only the lesser component of your daily sleep cycle: the midday nap.

Alcohol

Alcohol and creativity

Alcohol is a major enemy of a creative individual! In excess it is highly toxic to the brain! Even small doses can reduce the quality and the density of REM sleep. Alcohol also interferes with the function of deep sleep, produces sleep fragmentation, and relaxes the upper airway muscles, which worsens snoring, and severity of obstructive sleep apnea. Apart from its negative impact on sleep, alcohol reduces cognitive powers, inhibits memory encoding, and should be particularly avoided at times of creative effort!

Alcohol and health

To add confusion to the picture, lots of research indicates that small doses of alcohol may benefit health. Actually, a drink a day may be the simplest known method of preventing arteriosclerosis, heart attack, and cerebrovascular disease. There are reports that moderate beer drinking, or perhaps even alcohol in general, may reduce the incidence of Alzheimer's (Breteler et al. 2002[1]). A beer belly or aluminum in beer cans may have the opposite effect. In smaller quantities alcohol can improve the blood lipid profile, while, in contrast, excess drinking is associated with hypertension. Some physicians recommend daily alcohol in very small quantities (not more than a drink per day).

To a highly creative individual, alcohol poses then a health-vs-brain dilemma. Certainly it should be avoided 3-5 hours before sleep. It should also be avoided altogether before intellectual work if there is no intervening sleep period in between. This would leave place only for very moderate drinking in the early evening (assuming you do not do any brainwork later on) or before a siesta (i.e. assuming that this is the time you take a break from intellectual effort to take a nap).

Alcohol and exercise

Exercise is known to reduce drinking, possibly through its impact on the reward centers. However, it should also provide some protection against the toxic effects of alcohol on the brain. Exercise accelerates circulation and speeds up the conversion of alcohol into acetyl-CoA that can then be quickly used as a source of energy. This prevents a buildup of acetaldehyde that is the most toxic metabolite of ethanol. Acetaldehyde is partly responsible for the hangover and may have carcinogenic properties. Exercise also helps you reduce the level of blood triglycerides that might increase as a result of chronic drinking. Regular moderate drinking improves the metabolic machinery used to neutralize alcohol. On the other hand, binge drinking is equivalent to destroying one's own brain. If you ever get to the point of slurred speech, or experience a hangover, you know that bad things happen to your brain! The younger you are, the more damage you can expect!

Alcohol and sleep

Alcohol may accelerate sleep and bring a faster descent into deep sleep EEG, however, little is know about the structure of sleep induced with alcohol as EEG is only an approximate indication of the sleep stage. There can also be an increase in alpha waves which indicates that the function of NREM sleep might be disrupted This reference is used to annotate "I would never send my kids to school" by Piotr Wozniak

(Chan et al. 2015[2]).

Alcohol is quickly metabolized, and produces an acetaldehyde rebound effect that will greatly increase chances of waking up during the night. This effect keeps alcoholics up at nights, deprives them from REM sleep, and may actually be responsible for delirium tremens or perhaps even Korsakoff psychosis. Even moderate amounts of alcohol will have a noticeable effect on the quality of sleep! Make sure that alcohol is out of your system before your night sleep! Reading a book before sleep may be as effective as a glass of wine!

A great deal of confusion comes from the fact that very small doses of alcohol may have a very different impact on the brain. The impact will also be radically different in alcoholics in withdrawal. Nevertheless, you can safely employ the following rule of the thumb:

It is a very bad idea to pickle your brain in alcohol overnight

Alcohol and learning

You should never drink before creative work or learning. Even a gulp of beer can affect your performance. Some users of SuperMemo claim they enjoy moderate drinking while learning in the evening. This is understandable if the function of evening learning is fun and relaxation without great expectations as to the learning effect itself. I am not sure if this worsens or alleviates the impact of memory overload on the hippocampus, and the adjoining networks. However, I know for a fact that the memory effects will be greatly reduced due to the descending evening circadian slope and due to the effect of alcohol itself. The only imaginable benefit might come from suppressing the remnants of stress from a hard day of work.

Drinking rules

Some drinking rules you might consider:

  • alcohol in the blood before the night sleep will seriously reduce the quality and function of sleep
  • alcohol suppresses creativity
  • alcohol suppresses learning
  • hangover is bad for the brain and indicates a toxic impact of alcohol and its metabolites
  • you cannot expect health benefit it you consume alcohol to the point of slurred speech or balance problems
  • if you violate the excess rules (above), take a month-long break from alcohol to prove to yourself that you are not on the way to addiction
  • try to balance each drink with at least one hour of exercise to protect the brain. A beer after marathon might actually be healthy

Read more: Alcohol: Health Benefit or Hazard?

Caffeine

Caffeine is the number one drug used against sleepiness! 90% of Americans use it in some form. It can be found in coffee and coke, as well as in smaller quantities in tea and chocolate. It is addictive and acts via similar channels as amphetamines and cocaine. It also affects the reward centers (including the nucleus accumbens (Goldberg et al. 2002[3])). As caffeine has a profound effect on the central nervous system by blocking adenosine receptors, it is widely used to tackle drowsiness. However, majority of people little realize that it works well in your struggle with the adenosine-related homeostatic component of sleepiness, while it is quite inefficient in overcoming circadian sleepiness! Moreover, used against the latter, it can actually be quite unhealthy! If you abuse caffeine or use it at the time when your body clock tells you bedtime, you will only experience the symptoms that gave caffeine all the bad rap. These include: heart arrhythmia, irritability, overwhelming tiredness, depression, increased risk of miscarriage, and a typical coffee abuser's "sickness in the stomach". No wonder the popular myth says that coffee is bad for health and can contribute to a heart disease.

Surprisingly, the research on the health effects of caffeine does not seem to confirm its harmfulness. Considering the way coffee is manufactured, it may seem surprising that its carcinogenic effect is insignificant. Some publications even indicate a positive impact of coffee on health and longevity. If the research seems contradictory, it probably comes from the fact that some people drink coffee at the "right time", while others try to compensate for sleep deprivation or to mask circadian sleepiness. The link between coffee and heart disorders is weak, may depend on individual genetic ability to metabolize caffeine, and may be attributed to caffeine abuse in the form of excess doses or wrongly timed doses. Some research has even found that 3-5 cups of coffee are optimum for lifespan. The same research was criticized for failing to notice that coffee is more popular in well-to-do households that favor longevity. There have also been reports of positive impact of caffeine on memory. Caffeine increases the levels of BDNF in the hippocampus, and might perhaps boost neurogenesis. It was found to be modestly preventive against the Alzheimer's disease. You can then assume that caffeine is rather harmless in smaller 200-400 mg/day quantities (equivalent of 2-4 cups of coffee). Note that 50% of Americans take more than that. For caffeine to be harmless, it must be taken at the right time!

Caffeine tends to drive many people into a vicious circle: you drink it, you get a boost in epinephrine, you feel more energetic, you get a boost in dopamine, you feel better, you feel you can stay up late, you sleep less, you are more sleepy on the next day, so you need more caffeine, due to downregulation you get less boost per cup, you wonder why it does not work this time, you increase the dosage, and the vicious addiction circle continues. Coffee drinkers may occasionally experience migraine-like headaches. These are caused by an increased activity of adenosine receptors on days when the supply of caffeine is less. This results in the dilation of blood vessels in the brain. Vasodilation or activation of purine receptors on sensory neurons produces the headaches. Half a normal dose of caffeine should help. Conclusion: if you want to go straight on coffee, do not go cold turkey. Allow of a couple of days for your body to gradually fight off the addiction. A rational approach to caffeine is: use it as a circadian enhancer! Even though I always advise to avoid using substances in regulating sleep, you can use caffeine to accelerate your transition from sleep to full mental alertness. Small dose in the morning will shoot your alertness slope up and the regular intake will produce mild addiction that should help you fall asleep in the evening. This approach should be largely neutral to your health, to your sleep architecture, and positive to your alertness (at least very early in the day). Never use caffeine to cover up for insufficient sleep! Current knowledge about caffeine supports the recommendation for a cup of coffee in the morning in otherwise healthy individuals. As black coffee can be irritant to the stomach lining, coffee should rather be drunk with milk or cream. In regular nappers who do not battle insomnia, the circadian rhythm should yet permit drinking coffee immediately upon waking up from an afternoon nap.

As an arousal drug, caffeine may induce insomnia. This is why it should never be taken later than 6-7 hours before sleep. Caffeine half-life is about 6 hours for a healthy individual, but can vary substantially from person to person! Taken too late, caffeine will suppress REM sleep with detriment to the quality of sleep and its effect on memory. At the same time, when taken regularly early in the day, it may actually produce mild withdrawal effects and promote sleep. Its impact on sleep structure should also be minor if administered early enough, however, even a morning intake will reduce deep sleep in the night (Dijk et al. 1995[4]). Caffeine cannot serve as a weapon against sleep deprivation. Only a sufficient amount of night sleep can play that role. Caffeine should also not be used against the circadian sleep component. As argued throughout this article, circadian rhythm should best be left alone to run its course!

Some sleep experts recommend coffee before a nap to shorten its duration and/or to ensure waking during Stage 2 NREM. This may be ok in case you need a quick restorative nap in a hurry, e.g. in case of a drowsy driver. However, an optimum nap in a free running cycle will naturally last no more than 30 minutes, esp. in conditions of stress. The effect of napping may be short-lived if the nap is artificially cut short with a cup of coffee.

The only good time for drinking coffee is in the morning! (or after a nap in habitual nappers)

Never drink coffee to overcome circadian sleepiness!

Dr Stickgold says:

In all likelihood, the vast majority of people drinking coffee in the morning are doing so, consciously or unconsciously, to correct from sleepiness due to inadequate sleep quantity or quality"

It does not need to be the case. Even after a good night sleep, without sleep deprivation, coffee can crank up the creative powers of the brain. However, it most likely does so at the cost of attention. It may then help in creative problem solving, but it might also reduce one's attention during a morning lecture or magnify the effects of a stressful situation. Ultimately, you need to be your own judge and see if this is really your best morning drink.

Sleeping pills

Michael Jackson was a genius. He obsessively cared about his health. He wanted to be immortal or at least live past 150. He even contributed to a rumour that he slept in an oxygen tent to combat aging. And yet he committed a cardinal mistake of sleep hygiene: he used medication to control his sleep. This is why he died at 50. He could afford the best medical advice, and yet the genius of pop died of ignorance.

Millions of people on this planet take benzodiazepines to get themselves to sleep. Others drink themselves to sleep. Yet others take a puff of marijuana. Inevitably, the outcome is the same: unrefreshing sleep and daytime tiredness. Dr Kripke showed in his research that people taking sleeping pills die younger. Why then do so many people make the mistake of medicating sleep? For many, unrefreshing sleep is better than no sleep at all. More importantly though, as society, we have lost the true sense of what a refreshing night of sleep can do to our brains and bodies! All this damage is done at a time were very little is needed to get great sleep in a majority of healthy people:

  1. sleep at the right time, and
  2. sleep until you wake up naturally (for more see: Formula for good sleep).
Wherever possible, avoid sleep inducing medication. Even a seemingly natural product, melatonin, is not without its downsides. Read about free running sleep instead.

Melatonin

Melatonin is the only proven natural sleeping pill with few documented side effects. No wonder it is getting more and more popular. In addition, its antioxidant properties have sparked interest in melatonin as an anti-cancer agent. In the wake of such interest, there is always a wave of cheap counterfeit drugs hitting the market, esp. via the Internet sales. Those may contain no melatonin whatsoever.

Melatonin is a natural sleep hormone synthesized in the pineal gland from serotonin by acetylation catalyzed by serotonin N-acetyl transferase to form acetylserotonin that is later methylated with participation of SAM to melatonin. Melatonin is released during that part of the circadian cycle that corresponds with the period of darkness in both nocturnal and in diurnal animals. Diurnal animals, like us, are those that are active during the daylight period. However, melatonin is only an intermediary in the complex process of sleep onset. It can accelerate the onset, and can slightly advance the sleep phase, however, it cannot produce sleep on demand, and the sleep it can trigger will often differ in structure from a normal healthy sleep. Melatonin's impact on sleep structure is probably the reason why many people who use melatonin as a sleeping aid report feeling less refreshed in the morning. The explanation of its limitations may be in the fact that melatonin is produced downstream from the SCN, and as such cannot be considered a universal sleep hormone that affects the root of the sleep onset mechanism. Melatonin produces phase shifts along its unique PRC:

Phase response curves for light and for melatonin administration

However, it is not clear to what degree the phase shifts induced by melatonin are a result of the direct impact on the SCN where most of the receptors for melatonin reside, and to what degree it is a result of the phase shifting impact of the arousal in earlier waking (in evening administration). Whatever the answer, sleep induced with melatonin is not likely to be physiologically equivalent to natural sleep due to the bypassing of some of the stages of the circadian control. I guess it might be compared to sleeping in a slightly earlier phase with corresponding changes in the sleep structure.

Doses of up to 0.3 mg raise the serum melatonin to its natural nocturnal level. The half life of melatonin is around 40 minutes, which is important to know when timing melatonin administration to induce a circadian phase shifts. Side effects of high dosage of melatonin (above 1 mg) include cognitive impairment, drowsiness, nausea, headaches as well as troubling dream imagery. It is not clear if the negative impact of melatonin on cognition is caused by its effects on sleep structure or a direct effect of melatonin on the brain and/or other tissues. High doses might be counterproductive as they could produce phase delays caused by prolonged action on the delay side of the PRC that begins pretty early in the subjective night. Needless to say, for the same reason, additional administration on a sleepless night would act in opposition to the desired effect as compared with a timely evening use.

Melatonin can be used to remedy phase shifts in DSPS, however, it cannot be considered a cure. For its effects to continue, it requires continuous administration. The withdrawal might actually worsen the symptoms due to various downregulation issues and suppression of the endogenous release. Total sleep time does not increase while the subjective alertness may actually drop (Sack et al. 2007[5]). Melatonin has also been considered for morning administration in ASPS, however, considering its impact on cognition, this application would almost certainly prove highly controversial.

For a creative individual, melatonin should only be used when absolutely necessary (e.g. in order to generate phase shifts needed to maintain a schedule needed to function in society). The timing and dosage are essential for the therapeutical effect. Those must be consulted with a qualified professional!

Nicotine

Smoking destroys sleep, destroys health and kills many good people all too early. Do you think Obama is a cool and rational customer? Note that he is in a powerful grip of nicotine addiction. Even though he claims to have quit just in time to be president, rumour says he still takes a secretive puff from time to time.

For the sake of good sleep and good health, quit smoking now!

Did you hear of a great method for quitting smoking called the "incremental withdrawal"? Probably not. I coined the term on the spot. However, I saw many people succeed using this method. This is how it goes:

  1. Count exactly how much you smoke per day. Let's call that number Baseline Count
  2. Take 95% of the Baseline Count and call it your Current Count
  3. Every morning, make sure you put your Current Count into a cigarette box. Plan it as you wish, that box must be all you smoke on that day!
  4. Do you feel any better on your 95% level? Do you feel you could sustain this indefinitely? If you feel strongly about those questions, reduce your Current Count by one.
  5. Stick with your Current Count until you are really in a mood to make another step forward. Remember that reducing Current Count by more than one is risky to your resolutions. Remember that it makes sense to go through a whole constellation of days in your schedule (e.g. workdays vs. weekends) before you reduce your Current Count. Don't leap ahead before you are sure.
  6. Go back to Step 3 and stay in this cycle until your Current Count drops to zero. Remember that the key to success is always feeling great about the procedure. You need to sense progress, and enjoy it without suffering too much of withdrawal consequences.

I like the incremental withdrawal method because it increases the chances of success. In addition, cold turkey is not without risks. Quitting is always great for your cardiovascular system. However, withdrawal can put a tremendous stress on that system. It can actually kill you! I favor methods that fiddle less with dangerous aspects of human physiology. If you really want to prove your strength, go fast through the incremental procedure instead of quitting instantly. Quitting cold turkey is not only risky, it also increases the chances of a relapse. This is due to the immortal maxim: Easy come, easy go. Some more tips: How to quit smoking?

If you still cannot live without nicotine, Nicorette chewing gum may be the simplest over-the-counter way to tackle the addiction without the carcinogenic effect of cigarettes. Obama swears by Nicorette. Still Nicorette may even be more addictive than cigarettes on their own, and the short half-time of nicotine may result in overnight craving that disrupts sleep!

Remember that smokers usually experience a shallow and unrefreshing sleep. Smokers get less REM than non-smokers! Even though nicotine make you feel more creative, without REM sleep, your creativity and problem solving capacity will inevitably drop. Don't get fooled by the transitory effect of nicotine injections! You will be less smart in the long run! Nicotine will improve your alertness by acting on cholinergic receptors in arousal areas including an important sleep center, basal forebrain (see: Why do we fall asleep?). However, it will also cause night time withdrawal effect that often results in premature awakening. Do you often wake up after just 2-4 hours of sleep? If you quit, you might leave those premature awakening behind.

Interestingly, only 4% of users of SuperMemo are smokers (source). In addition, users who smoke spend much less time on learning with SuperMemo (an average of about 10 minutes per day as compared with the usual average of around 30 minutes). This is more related to the hormonal balance in the brain of a smoker than to smoking itself. Smokers simply do not have the patience for SuperMemo and are less likely to be in-depth learners. Yet there are strong indications that those who quit smoking show improvement in their perseverance in learning! That is one more reason to quit!

Exercise

Exercise is good for sleep

If employed skillfully, exercise is a blessing for sleep. Exercise is good for health, and whatever is good for health is also good for sleep. Exercise is known to enhance deep sleep and promote the nocturnal release of growth hormone, which has been found to stimulate memory consolidation via its impact on protein synthesis. Exercise, deep sleep and GH have all been linked with neurogenesis (i.e. brain growth). A good night sleep following exercise causes an increase in release of BDNF and an increase in nerve cell proliferation (for example see: Running increases cell proliferation and neurogenesis in the adult mouse dentate gyrus (Van Praag et al. 1999[6]), Sleep deprivation reduces proliferation of cells in the dentate gyrus of the hippocampus in rats (McGinty et al. 2003[7])). In other words, exercise builds both muscles and the brain! (Gambelunghe et al. 2001[8]).

Sleep, learning and exercise are the best friends of a smart brain!

What is the best time to exercise?

There are different forms of exercise: the type, the intensity, and the timing will affect sleep. The number of possible permutations is huge. It would take another article to list them all. Read about your favorite form of exercise, and experiment on your own! I tend to favor exercise at the descending slope of the circadian curve, either before lunch or dinner, or in the early evening. This choice is dictated by the wish to preserve the period of highest alertness for creative work. In addition, peak alertness times are not necessarily peak physical performance times that come at a slightly later phase. Metaphorically, the brain wakes up faster than the cardiovascular and, most of all, musculoskeletal system. Exercise before a siesta-time meal can deepen the mid-day nap as long as there is sufficient "cooling" period. Late afternoon exercise might be best for exercise's sake. Endurance and strength tend to peak at that time while the chances of injury are lowest (one theory says that it is due to the least catabolic testosterone/cortisol ratio). Early evening exercise, if not too intense or injurious, will do wonders to the quality of night sleep. Moreover, evening exercise seems like a good filler for the time when the brain is already winding up its capacity for mental effort. Exercise may increase the demand for sleep even more than learning. However, high adrenaline, competitive, emotionally charged, or injurious exercise that comes too close to the subjective night sleep could be disruptive and reduce the quality of sleep. Also, with some exceptions, it might not be as healthy as exercise at a more suitable circadian phase. Late exercise may increase the risk of injury. It can also result in contradictory signals for the cardiovascular system that is also supposed to wind down for the night. Exercising before sleep is little less contradictory than exercise after a meal. This way a late evening marathon should be discouraged, while some calisthenics or moderate body building might be encouraged. Again, your own experimentation is essential. If your way of exercise feels great, and your creative work does not suffer, and you sleep great, chances are you are doing all things right, and you are more likely to persist in your exercise regimen for psychological reasons. Early morning exercise is great for people who battle with sleep phase problems. If you find it difficult to fall asleep early enough and need to resort to an alarm clock due to oversleeping, early jogging in bright sunshine can help you shift the sleep phase. Exercise and light are powerful zeitgebers. Naturally, this practise will also contribute to your running out of mental energy earlier in the day, which, at times, is exactly what you need to remedy sleep phase problems. Republican presidential candidate Ron Paul confessed that the best time for exercise for him is the very early morning. He regularly takes long walks at the start of the day. This may work for him as walking is not injurious and can indeed be taken on very early in the morning. Moreover, for a politician, this exercise does not need to quarrel with his creative regimen. Walking is great, for example, to reiterate main talking points for an evening debate. Paul's example shows that there is no one-for-all cookie cutter rule for everyone. Late evening exercise, for example, tends to delay the sleep phase and might be helpful in people suffering from ASPS.

Formula for best exercise

If you anticipate your exercise with enthusiasm or even euphoria, you know that you chose the right type, timing and intensity. If you feel pleasantly exhausted, if you fall asleep fast, and if your sleep is deep, you know that you are doing things right. If you cannot drag yourself for a jogging, try walking, or swimming. If water is too cold, perhaps try swimming in an indoor pool. If swimming is not challenging enough, try the adrenaline of team sports. Or perhaps a social setting of a gym will suit you better. If exercise worsens your insomnia, try it earlier, change the intensity, or the type of exercise (e.g. to one that is less injurious). Read relevant exercise tips (rehydration, preventing injuries, etc.). Exercise can be and should be addictive. Many people hate exercise because they never tried it properly. If you are one of those, try again, perhaps with a personal trainer (for a while). People hate exercise only if they do not know how to exercise!

Listen to your body! Exercise should make you enthusiastic before, and contented afterwards. If that's the case, you are almost certainly on the right track.

Sleep is good for exercise

It is well-known, at least amongst body builders, that sleep is necessary for muscle growth and repair. If you do not get enough sleep, your body building effort will be ruined. The muscles need sleep, but we do not sleep because of the muscle needs. For the organism to cope with muscle regeneration, there is no need to shut off the central nervous system, and make one unconscious for a third of one's life. If REM paralysis was to play this role, it could be enforced at the level of the medulla oblongata without making us unconscious. If growth hormone secretion was to play a role, it can also be upregulated in abstraction from the state of the central nervous system. There are many other benefits of sleep for muscular regeneration but none will require the state of unconsciousness on its own. For evolution, using sleep for muscle regeneration would be as sensible as shutting down the government in order to fix a highway. The universal belief that sleep evolved to promote rest and regeneration comes from the feeling of being "broken down" and "unrefreshed" once you do not get enough sleep. However, you do not feel crushed after an all-nighter because of the damage inflicted by the lack of sleep. Your state is simply your body's own defense against not getting enough sleep. You can cheat those defenses to a limited extent. One night of good sleep, and your body seems to be back to shape. The only true damage inflicted by sleep deprivation is to the fabric of memory. Unfortunately, this damage is imperceptible, and the universal perception is that sleep is cheap and can easily be dispensed with. Whether you sleep for the sake of your memory or for the sake of your muscles, sleep is good.

Sex and exercise differ

Someone noticed that I contradict myself recommending sex before sleep and saying that exercise directly before sleep is not recommended. One only needs to observe that hormonally sex and exercise differ like chalk from cheese, the degree of stress in sex should be negligible (at least in a stable and harmonious relationship), chances of injury are not too high, etc. This kind of exercise before sleep I wholeheartedly recommend.

TV

Many sleep experts say that a bedroom should only be used for sleep and sex. They also imply that there should be no TV in the place where you sleep. However, this advice seems to stem from a futile battle against sleep-onset insomnia that is so often caused by sleep phase problems. If you go to sleep very early, and you are not sleepy enough, it is quite natural that a TV or radio could provide a distraction or even wake you up prematurely (e.g. with an annoyingly loud advertising). The effect of a TV sound may be quite different when you sleep in the right phase (e.g. in free running sleep). In those circumstances, you go to sleep when you are really ready. If you run a pre-recorded material, and set the timer to turn the TV off in 5-15 min, you might be actually doing your sleep a good service. An important thing for a good night sleep is to leave all issues of the day behind. Even pleasurable thoughts related to your life can keep you up and excited. At the same time, repetitive news from foreign lands or a moderately interesting science program can effectively lull you to sleep in 2-4 minutes, which should be your healthy target. Some TV or radio news for an adult can be compared to soothing music for a newborn or a fable that mom reads to a child before sleep. This has even become a part of bibliotherapy. Many people read themselves to sleep, which is a good idea (as long as passionate reading does not go on till morning hours). An audio-book might also be effective in a different way. It is a very personal issue. You need to test it for yourself and avoid the dogma. If you need to wake up early and you have problems with falling asleep, you may follow the conventional advice. However, if you can afford to run your sleep free, you should go to sleep only then when you are truly sleepy. In those cases, to TV or not TV, is really not a question. You can get those 2-3 min. of news, or just fall asleep in absolute silence. It is up to you.

Cannabis

Marijuana is a well known sleep "remedy". It is particularly popular among DSPS sufferers who claim it helps them go to sleep earlier. Unfortunately, research seems to indicate that cannabis changes the structure of sleep (e.g. reducing the proportion of REM sleep (Feinberg et al. 1975[9]; Fujimori and Himwich 1973[10]), which can also be expressed by particularly lucid dreams in withdrawal). This results in lesser sleep efficiency and possible premature awakening after the administration of cannabis. Due to the suggested impact on the release of melatonin, soporific effect and possible premature awakening, cannabis might seem like a remedy that might stabilize the circadian cycle in DSPS. However, this stabilization would be achieved at the cost of quality of sleep and productivity. Subjective sleepiness reports seem to indicate that indeed marijuana smokers do wake up much less refreshed. Moreover, they experience unusually high energy levels and rich dreams in withdrawal, which is an indication of the negative impact of the drug on the quality of sleep.

In abstraction from other potential negative health effects of smoking marijuana, it should definitely be avoided in the "protected zone", i.e. in the hours preceding sleep. In that respect, it is not much different from alcohol or benzodiazepines, which are also well known to affect the sleep structure and the efficiency of sleep. The same rule applies in all these cases: treat your brain before sleep no worse than you treat your brain before creative work. Whatever is bad for creativity is likely to be bad for the quality of sleep.

Dr Buzsaki spoke in an interview: "Timing and network synchronization are the essence of all cortical computation, and the timing ability of cortical networks is reflected in the rhythms they produce. We have shown that deterioration of synchrony of hippocampal assemblies, e.g., induced by the active ingredient of marijuana, is reflected quantitatively by the field rhythms. In turn, the degree of impaired hippocampal oscillations is correlated with the deterioration of memory performance. [...] Oscillations constitute a robust phenotype that reliably 'fingerprint' an individual and expected to alter in most psychiatric disorders. Often such changes are most pronounced in sleep".

Sex

Sex is good for sleep, however, using sex as a "sleeping pill" may not be too good for sex itself. For circadian reasons, morning sex should be best (in free running condition). Testosterone peaks in the morning. However, sex is a powerful hypnotic, and morning sex may undermine morning alertness. On the other hand, sex before sleep is likely to help you fall asleep faster. Evening sex may be less "efficient". You are more tired and perhaps not in a mood. But sex is a great soporific! Sex is a very personal thing, but I believe that creative people perform better if they sexercise before sleep or at siesta time.

If you practice sex without procreative intentions, positive influence of sex on sleep may be your number one excuse for sticking faithfully to your conjugal duties. Here is also a recommendation to stick with a single partner. Longevity studies show that healthy stable monogamous sex life is one of powerful life expectancy determinants (even though, in this case, monogamous should stand in opposition to promiscuous rather than to polygamous). While monogamous sex is generally good for sleep, sex with your new great love may actually disrupt sleep. Apart from a healthy dose of endorphins, it will also raise your catecholamines that may fragment sleep cycles. For the same reasons, promiscuous sex may also fail to play the expected hypnotic role.

Many highly creative people opt to sleep in beds that are separate from their partners. This approach may undermine family cohesion and sex life, however, it is pretty understandable, esp. in people who love to burn the candle at both ends. Co-sleeping is probably a better choice healthwise as long as it does not affect the quality of sleep. In addition, both partners should sleep in similar hours and forgo the alarm clock. This is a hard personal choice that needs to balance a healthy tradition with the quest for productivity. I do not think I can recommend one choice over the other. It is too complex and too personal.

Diet

Foods that we eat affect our alertness, and our propensity to sleep. However, the role of foods is largely overappreciated. For example, it is very difficult to significantly affect the circadian cycle with basic foodstuffs. It is the timing of meals that may matter more. Homeostatic sleepiness can be enhanced with some foods, esp. when consumed in larger amounts. However, this is highly individual. For example, your glucose tolerance will determine the effect of glucose-rich foods. Your ability to metabolize alcohol or caffeine will determine the degree of the effect of these two frequently consumed mind-altering substances. Your food intolerance and food allergies can have a big impact as well. Your current satiety status, rehydration, caloric needs, etc. also play a role. Ages old recommendations, such as "a glass of warm milk before sleep" will only play a marginal role in helping you sleep well. It would take a separate article to describe all nuances and possible interactions and synergies. I will therefore limit this section to the following basic rule-of-the-thumb mnemonics:

  • whatever is good for health is also likely to be good for your sleep (at least in long-term). Healthy body will ensure healthy sleep. Consult your favorite healthy diet book or website. Keep learning! You need to virtually memorize an encyclopedia of foods to truly understand all nuances of different diet choices.
  • if you are on an obese side, avoid meals in the last third of your waking day. For hormonal reasons, this will help you keep your weight in check, and help you sleep better.
  • even if you are on a weight loss program, before creative work you need foods that will gradually release glucose into the bloodstream while you work in high gear
  • avoid alcohol and caffeine in the last third of your waking day
Your best diet for good sleep is roughly the same diet that is good for your health and longevity.

Variations in the healthy diet are unlikely to have a major impact on your sleep. You may only want to watch caffeine, alcohol, exotic herbal products, toxins, and all substances with a substantial effect on the nervous system. Otherwise, the diet should have only a minor impact on the demand for sleep, circadian patterns, homeostatic sleepiness (with a major exception of caffeine), progression of sleep stages (with a major exception of alcohol), or neural efficiency of sleeping. The reason for this is the same as in many other cases of homeostasis: the organism is striving at retaining the homeostatic balance throughout all systems. Rare foods, herbal preparations, pharmacological intervention, etc. can always change or unbalance internal equilibria, but a standard healthy diet is far less likely to do so. It takes an extraordinary nutritional error to stop the human heart. It is even harder to stop the gene-based body clock.

Vegetarian diet

Lots is being said about vegan or vegetarian diets in reference to sleep. It is not true that herbivores sleep less, as there are many exceptions to the rule (there are herbivores that sleep three times as much as short-sleep carnivores). There is, however, a correlation, which says that the decrease in sleep time is faster with the increase in weight in herbivores than it is in carnivores. In other words, heavy herbivores, like giraffe, indeed sleep very little. This correlation may be explained by changes in metabolism, but it could also reflect a different lifestyle. A predator may eat once and then spend many hours on digestion, an elephant keeps munching all day long to sustain its energetic needs, while a gazelle needs to maximize vigilance to ward off an attack from a long sleeping lion. The correlation between the diet type (herbivore vs. carnivore) and the length of sleep links sleeping habits with eating habits of a species, not with eating habits of an individual. While humans are omnivorous, you won't become an herbivore, and allegedly a short sleeper, by enforcing new eating habits.

Sleep and glucose metabolism

While changes to a healthy diet do not have much impact on the quality of sleep, sleep has a powerful impact on the metabolism. Sleep deprivation research tells us that adequate sleep is particularly important for healthy glucose metabolism. Sleep deprivation, shiftwork and jetlag all facilitate obesity and the development of type II diabetes. The possible reason is that sleep deprivation decreases leptin and increases ghrelin for the same caloric intake (Knutson et al. 2007[11]). Those two hormones control the appetite and affect the homeostatic set point for the body fat level. In sleep deprivation we tend to eat more and achieve satiety at a point which will increase the body fat percentage. In caloric terms, those changes can be pretty dramatic. Halving one's sleep might increase the demand for food by 1000 kcal per day. There are also indications that the appetite switches to substantially favor high carbohydrate foods. This only magnifies the problem. Last but not least, sleep deprivation simply makes you lazy. You are less likely to expend those extra calories.

Getting sufficient sleep helps you stay slim!

For more see: The Dream Diet: Losing Weight While You Sleep.

Fasting

Most nutritionists will tell you that weight loss is easier if you avoid larger meals in the last third of your day. Others claim this is a myth. Epidemiological studies, as always, do not provide a clear cut confirmation. Ramadan fasting seems to favor weight loss despite nighttime eating. Controlled studies also provide seemingly contradictory outcomes depending on the design. The conviction that evening fasting might be beneficial probably originated in the 1970s when weight loss programs were shown to prove more effective when meals are eaten in the first half of the day, as opposed to the second half (for a discussion see: Weight Loss is Greater with Consumption of Large Morning Meals and Fat-Free Mass Is Preserved with Large Evening Meals in Women on a Controlled Weight Reduction Regimen (Keim et al. 1997[12])).

I believe that if you try evening fasting for yourself, you will quickly discover that it can do wonders to your sleep, its restorative powers, your weight loss targets, your morning energy, etc. Unless you are in this ravenous group that cannot sleep without a nighttime trip to the fridge or at least an evening snack, you will also notice that for circadian and psychological reasons, evening fasting is pretty easy to sustain once you get the hang of it. Fasting promotes the release of ghrelin (Bloom et al 2000[13]), which contributes to the overall nighttime increase in the release of growth hormone (Norrelund 2005[14]). Most of growth hormone release occurs in deeper stages of NREM sleep early in the night. This nighttime release is partly responsible for the anabolic mode of early sleep that helps you avoid abdominal obesity, strengthen your bones, rebuild your muscles, tendons, ligaments and other tissues subject to daytime wear and tear. Hormonally, evening fasting produces effects similar to those of overall calorie restriction, which has been shown to prolong life in mice. Older people seeking their youthful past may resort to growth hormone injections. Evening fast combined with a healthy free running sleep is definitely a healthier and simpler option. Try it for yourself, and if you have any doubts, please write to me.

If you are an insomniac or suffer from DSPS, you should also consider evening fasting as a factor that might help you maintain a healthy sleep schedule. See: Curing DSPS and insomnia. On the other hand, if you are troubled by early awakenings and short nights, you might defy a conventional nutritionist advice and listen to Seth Roberts who says the reverse. Roberts found that skipping breakfast helps him maintain a healthy sleep phase (Roberts 2004[15]). Thousands of people follow Roberts' advice without realizing that a majority of them are likely to be at the DSPS end of the phase disorder spectrum, and his advice, while well researched and ideally suited for him, may have the opposite effect in their own case. Remember therefore that your fasting choices as well as other lifestyle changes that affect your sleep must be chosen to fit your chronotype.

Combating jetlag with diet

There is some evidence that rats can entrain their cycles to food with the help of the DMH, however, using starvation to combat jetlag is only a theoretical concept. The SCN rhythm is not maleable beyond minor phase shifts, and losing synchrony between the SCN and the DMH, if at all possible in humans, is not likely to be a good thing for health, esp. that humans do not seem to have evolved a mechanism to subject sleep to the timing of the availability of food. If you happen to have any success in combating jetlag with the timing of meals, please let me know.

Learning

Few things can be as tiring before sleep as a dose of heavy learning. However, a leading sleep expert, Dr Dement, in his guide to better sleep suggests: "Avoid heavy studying or computer games before bed, they can be arousing". This advice needs a slight amendment. There is no doubt that computer games are arousing and should be avoided. However, "heavy studying" may have many forms. If you study for an exam, and this brings stressful images of the exam itself, it can indeed be arousing. If you study a fascinating subject that monopolizes your thoughts, it can be arousing as well. Similarly, learning in a brightly lit room may slow down the descent to sleep. However, if you extract the pure learning process devoid of stressful associations, light, social aspects, etc., you will come to a different prescription.

Learning should help you sleep

The more you learn on a given day, the lesser your capacity to learn more (see: Learning overload). For that reason, the more you learn, the faster you will get seriously sleepy. However, you will not be able to sleep well until your circadian subjective night arrives. This means that you can advance your bedtime only slightly, e.g. by 20-60 min. You cannot generate multi-hour phase shift with learning!

Learning is associated with the homeostatic component of sleepiness, and can promote sleep.

If you want to use learning as a form of getting tired for sleep, and you do not mind the learning process to be less efficient, here are the suggestions:

  1. select some unexciting learning material (e.g. your French vocabulary could pass the test, unless you plan an exciting trip to Paris)
  2. subtract the high priority material (learning in a drowsy state can negatively affect the learning process in that subset)
  3. make sure that your monitor and your room are not too bright. Otherwise you may impact your sleep phase that will make sleep harder on the next day

Remember that learning in a sleepy state is actually a violation of the learning hygiene. Science has not yet conclusively answered the question if this is good or bad for your memory in the long run (Wozniak 2002[16]).

Does learning increase total sleep?

Even though you may hear from me often that learning increases the demand for sleep, I have not been able to demonstrate the fact with SuperMemo data! I simply repeat what other scientists keep saying. Learning should indeed increase the demand for neural optimization in sleep, however, this may as well be done by increasing the intensity of processing (e.g. by increasing the density of REM sleep). Heavy learning may not necessarily increase the length of sleep. Learning may also be like exercise, it does not contribute much to the baseline demand. If you do not learn with a textbook, you still keep learning by noticing things, by thinking, by talking to people. If you do not exercise, you still burn lots of calories. It seems easier to prove that heavy exercise results in longer sleep than to prove that heavy learning increases total sleep. I have been able to show that learning contributes to homeostatic sleepiness. As such, it should contribute to earlier bedtimes and longer sleep. However, I still have no data to show it. For more see: How learning affects sleep?

References

  1. Ruitenberg A. MD, Van Swieten J.C. MD, Witteman J.C.M. PhD, Mehta K.M. DSc, Van Duijn C.M. PhD, Hofman A. MD, Breteler M.M.B. MD, "Alcohol consumption and risk of dementia: the Rotterdam Study," The Lancet / Volume 359 / Issue 9303 (January 26, 2002): 281-286
  2. Chan JK, Trinder J, Colrain IM, Nicholas CL,"The acute effects of alcohol on sleep electroencephalogram power spectra in late adolescence" Alcohol Clin Exp Res. / 39 (Feb 2015): 291-9
  3. Solinas M., Ferré S., You Z.B., Karcz-Kubicha M., Popoli P., and Goldberg S.R., "Caffeine Induces Dopamine and Glutamate Release in the Shell of the Nucleus Accumbens," The Journal of Neuroscience / Volume 22 / Issue 15 (August 1, 2002): 6321-6324
  4. Landolt H.P., Werth E., Borbély A.A., Dijk D.J., "Caffeine intake (200 mg) in the morning affects human sleep and EEG power spectra at night," Brain Research / Volume 675 / Issues 1–2 (March 27, 1995): 67–74
  5. Sack R., Auckley D., Auger R.R., Carskadon M.A., Wright K.P., Vitiello M.V., Zhdanova I.V., "Circadian rhythm sleep disorders: Part II, advanced sleep phase disorder, delayed sleep phase disorder, free-running disorder, and irregular sleep-wake rhythm," SLEEP / Volume 30 / Issue 11 (2007):1484-1501
  6. Van Praag H., Kempermann G., and Gage F.H., Running increases cell proliferation and neurogenesis in the adult mouse dentate gyrus, Nature Neuroscience / Issue 2: 266 - 270, doi: doi:10.1038/6368
  7. Guzmán-Marín R., Suntsova N., Stewart D.R., Gong H., Szymusiak R., and McGinty D., Sleep deprivation reduces proliferation of cells in the dentate gyrus of the hippocampus in rats, The Journal of Physiology / Volume 549 / Issue 2 (June 1, 2003): 563-571, doi: 10.1113/jphysiol.2003.041665
  8. Gambelunghe C., Rossi R., Mariucci G., Tantucci M., and Ambrosini M.V., "Effects of light physical exercise on sleep regulation in rats," Medicine & Science in Sports & Exercise / Volume 33 / Issue 1 (2001): 57-60
  9. Feinberg I., Jones R., Walker J.M., Cavness C., March J., "Effects of high dosage delta-9-tetrahydrocannabinol on sleep patterns in man," Clinical Pharmacology & Therapeutics / Volume 17 / Issue 4 (April 1975): 458-466
  10. Fujimori M. and Himwich H.E., "delta9-Tetrahydrocannabinol and the sleep-wakefulness cycle in rabbits," Physiology & Behavior / Volume 11 / Issue 3 (September 1973): 291-295, doi: 10.1016/0031-9384(73)90003-6
  11. Knutson K.L., Spiegel K., Penev P., Van Cauter E., "The metabolic consequences of sleep deprivation," Sleep Medicine Reviews / Volume 11 / Issue 3 (June 2007): 163-178, doi: 10.1016/j.smrv.2007.01.002
  12. Keim N.L., Van Loan M.D., Horn W.F., Barbieri T.F., and Mayclin P.L., "Weight Loss is Greater with Consumption of Large Morning Meals and Fat-Free Mass Is Preserved with Large Evening Meals in Women on a Controlled Weight Reduction Regimen," The Journal of Nutrition / Volume 127 / Issue 1 (January 1, 1997): 75-82
  13. Wren A.M., Small C.J., Ward H.L., Murphy K.G., Dakin C.L., Taheri S., Kennedy A.R., Roberts G.H., Morgan D.G.A., Ghatei M.A. and Bloom S.R., "The Novel Hypothalamic Peptide Ghrelin Stimulates Food Intake and Growth Hormone Secretion," Endocrinology / Volume 141 / Issue 11 (November 1, 2000): 4325-4328, doi: 10.1210/en.141.11.4325
  14. Norrelund H., The metabolic role of growth hormone in humans with particular reference to fasting," Growth Hormone & IGF Research / Volume 15 / Issue 2 (April 2005): 95-122, doi: 10.1016/j.ghir.2005.02.005
  15. Roberts S., "Self-experimentation as a source of new ideas: Ten examples about sleep, mood, health, and weight," Behavioral and Brain Sciences / Volume 27 / Issue 2 (April 2004): 227 - 262, doi: 10.1017/S0140525X04000068
  16. Wozniak P.A., "Can too much learning lead to Alzheimer's?" (May 2002)