- What changed in 5 years?
- Impact of the original article
- Polyphasic Women
- Why don't I try and see for myself?
- Sleep deprivation vs. alcohol abuse
- Free-running sleep cannot be compared to overeating
- Scientific challenge
- What is my agenda?
- Can battling polyphasic sleep hurt SuperMemo?
- What are my future research plans into polyphasic sleep?
- Are polyphasic sleepers dumb?
- Could polyphasic sleep work for mutants?
- BBC experiment
- Claudio Stampi
- Steve Pavlina
- Polyphasic sleep adaptation myths
- Circadian timing of naps
- Some chronobiological findings from SleepChart and SuperMemo relevant to polyphasic sleep
- Chronobiology vs. SleepChart +
- Polyphasic sleep vs. SleepChart +
Since the publishing of my original article on "polyphasic sleep", I received a lot of mail with requests to produce an update, esp. on conclusions coming from my contacts with young people attempting to implement a polyphasic sleep schedule. Quite a bit has changed in those five years, and those who would like to sleep polyphasically got far more opportunity and material to research the subject thoroughly and make right decisions. In this followup article, I would like to address the criticism of the original article, and write a few words about how the new tools made available in SuperMemo help study sleep and predicate on the possibility of sleeping polyphasically.
The present article is justified by a couple of changes that occurred in the last 5 years. Here are a few important contributors to my knowledge of the polyphasic world:
- I received some 500 pieces of mail and got in personal touch with many polyphasic adepts. Of those attempts that I was given a chance to monitor, all were unsuccessful. Some of the critics of the original article claimed that they do sleep polyphasically, but I received no data that could serve as the basis for verification. The most interesting conclusion coming from the mass of mail received is that people drift towards polyphasic sleep less as a result of their hunger for achievement, and more for their prior problems with sleep. They often think of polyphasic sleep as a panacea for all their sleep problems. This perception is magnified by multiple blog claims.
- I received a couple of SleepChart data submissions demonstrating how difficult the struggle with the polyphasic sleep is. Admittedly, I was quite impressed with the degree of determination some of those experimenters showed.
YouTube entered the scene and now anyone can see individual tribulations, black-ringed eyes, dishevelled hair, mumbling voices, and the plain torture of trying to stay awake. As always, there are always those who beam health, smiles and the declarations like "I now feel better than ever". Below I include a lovely example of a YouTube contribution; well done, cocky, honest, representative, funny, and iced with a positive ending:
- The newest version of SleepChart makes it possible to model the changes in sleep propensity. Even though the model applies to free running sleep, its application to polyphasic sleep provides a good illustration of the roots of polyphasic suffering.
- Some of polyphasic mythology seems to have died out. No longer do we hear much of Churchill or Jefferson sleeping polyphasically.
Overall, I consider the original article a success. When young men turned to me with a request to help supervise their experiments, I had to start from trying to dissuade them from the idea. I expected many refusals to be met with "No. I will still try. I need more time per day", but I got surprisingly many "I got sleep problems. If free running sleep might help, I will try it first. Sounds sensible". As I wrote previously, those are "rebellious men ready to seek new ways for maximum productivity". No scientific argument can be persuasive in such cases. After all, all reasoning can easily be quashed with "science does not have all the answers yet". None of the young rebels succeeded in entraining polyphasic sleep, yet some were persistent enough to provide some SleepChart data that sheds some more light on the implausibility of the polyphasic sleep schedule. This data can now be compared with sleep habits of young students who use SleepChart to better understand their own circadian cycle.
The mail that I have received was mostly critical, but it should not be used as a measure of success. It is not important what proportion of readers would agree with me. It is important how many gave up the idea of sleeping polyphasically as a result. Within the five hundred pieces of mail, I roughly estimate the distribution of their nature as follows:
- 50% - criticism of the article from the adepts of polyphasic sleep
- 40% - requests for help in implementing polyphasic sleep with the help of tools like SleepChart, etc.
- 10% - grateful mail of the sort "thank you for saving me lots of time and health. I wanted to try polyphasic sleep but, after reading the article, decided not to"
10% may seem like a very low conversion rate. However, this translates to hundreds of hours of someone's time. I am sure it also translates to some health benefit. For example, a great deal of polyphasic attempts end up with a cold or influenza, which must reflect the impact of this sleep schedule on the immune system.
What Aaron wrote is pretty representative of the 10% group: "The idea of sleeping in naps spread throughout the day intrigued me, as I have always suffered from what I was unable to properly quantify, but now know is DSPS. If I do not use an alarm clock, and go to sleep when I become tired, I see my sleep/wake times shift to significantly later times every day (hours later). This has been a constant source of frustration for me, and I considered a polyphasic schedule in order to help correct the problem. However, after reading "Polyphasic Sleep: Facts and Myths", I have decided this would be a sincere waste of my time".
More frequently, I was a bit less successful. For example, Joel wrote: "I am writing to ask for your guidance on my attempt at the "Uberman" sleeping schedule - whereby one sleeps 20 minutes at 6 evenly spaced times during a 24 hour period. I have read your arguments against polyphasic sleeping, but I'm set on attempting it. Your plea for people to contact you if they are considering it is what motivates me to email you now as I'm interested in my potential discomfort being beneficial to sleep research. I'd like to volunteer to log my attempt with your sleep chart software and answer any questions you have about my experience".
Criticism would usually skirt around the science argument and quote from blogs of people who claim they have succeeded with polyphasic sleep. For example Kop wrote: "There are MANY people who successfully adapted. [...] You simply neglected to cite them, and you cited only people who failed. I think this is very unfair and misleading to your readers. I may sound like a broken record, but even if you believe that everyone who claims to have been successful is lying you should let your readers make this choice and you should definitely not just completely leave out all the information you personally don't agree with".
At the extreme end of the range, there was mail from George who straightforwardly accused me of lying: "It is important to realize that most of the experimenters are Americans, because apparently you don't understand the dynamics of our culture. Briefly put, you paraded evidence that seemed to support your claims, while completely ignoring evidence that does not. For example, you flatly state that no polyphaser is ever a woman, while at the same time quoting from a blog written by one! (A search at YouTube.com will reveal other female polyphasic sleepers.) In another instance, you quoted a medical disclaimer from one polyphasic, while leaving out his comments on the experiment's great success. This practice on your part, Doctor, is seen by Americans as being dishonest. Dishonesty by a scientist completely ruins credibility. Since it's easy to believe that you were dishonest on polyphasic sleep, it's also easy to believe that you are lying about your product, SuperMemo. This is going to cost you money, Doctor. Who is going to buy a product by a lying scientist?
Most importantly, polyphasic sleep mania did not grow exponentially as I feared. It reached some plateau and its population includes fewer true experimenters and more zany characters that won't be persuaded by any means except their own perpetual failure. I am then proud that my voice is relatively loud among the few who spoke against the practise. Sleep researchers are too busy to study freak ideas. Doctors do not perceive it as a danger as they are pretty unlikely to meet an actual victim. You need the magnifying glass of the net to see the worldwide size of the phenomenon. Thus efforts of a goodwilled activists grow in relative importance.
My greatest mistake committed when writing the original article was to inadvertently use the word "invariably" instead of "predominantly". As a result, it seems like half of the critical mail accused me of distorting facts by claiming that there are no women who tried to sleep polyphasically. Some even went as fast as to claim I discredit or disparage women!? For starters, if this was to be a lie, it was a pretty lame one, I even quoted from polyphasic blogs written by ladies. There is nothing to stir people's aggression like a lame lie, and if I committed one, I would have to be tossed into the dumbest liars category. Secondly, should my claim not rather be interpreted as "Ladies are too smart for this. Only guys start wars and apply crazy sleep schedules". Retroactively, I corrected the unfortunate word at the risk of getting fewer inspiring pieces of mail from the less tolerant or the less inquisitive range in the reader spectrum. Ah yes, just in case, I did not spell it clearly enough: there are women who think sleeping polyphasically is a good idea!
Very often I am being asked how I can claim any authority on polyphasic sleep without ever trying it myself. For starters, I do not claim to be a polyphasic sleep expert. As a humble biologist, I simply need to recall the ABC of chronobiology to figure out that polyphasic sleep is not feasible. You do not need to be a junkie to study drug addiction, even though a glass of vodka might be a recommended one-time treatment to an abstinent investigator of alcoholism. I understand the pain of the alarm clock because I used it sparingly during my university years as well. I understand the pain of jet lag and sleep deprivation from my early turbulent years of involvement in the SuperMemo business. However, I need a fresh brain for my work. Even one day of a hazy mind is a loss. I cannot possibly hope to struggle through a polyphasic routine in hope of proving that the elusive and ever remote "adaptation" is just an urban myth. If someone told you to lie on the railway tracks with a promise of being struck by nirvana, you would refuse. For you know with sufficient probability that the outcome would more likely be pretty gory.
Sleep researchers love to compare sleep deprivation to intoxication: both disrupt one's self-assessment abilities. Like an alcoholic who always claims "I am not drunk. I am just inebriated", a sleep deprived person will often say "I am fine. I am crisp and alert", while his or her ability to perform mental tasks may be seriously impaired. Driving when sleep deprived may be as dangerous as driving while intoxicated. This loss of self-assessment capacity may in part explain why so many polyphasic bloggers tend to claim they have adapted. They tend to write about their success at the moment of lucidity or euphoria (see the chronobiology insert on how this can be explained with the two-process model of sleep), while ignoring those brain dead moments as "temporary setbacks", transitory adaptation state, etc. In those hazy moments, a blogger may be unwilling to update the blog, magnifying the bias as perceived from the outside. Adaptation to polyphasic schedule is not possible, but this self-assessment handicap is just one of many reasons that boastful bloggers need not be branded as liars on the sole basis of their claims. Perhaps it is even possible to flatten or desynchronize the circadian function bad enough to lessen the average pain. Needless to say, with all genetic cascades resting on the circadian cycle, such an outcome can only lead to a health disaster. It could be likened to applying contradictory stimuli to the gut in order to prevent the natural progression of peristalsis. What a polyphasic sleep adept is risking at such point is an outcome comparable with the fate of Mr Creasote in the "Monty Python's The Meaning of Life" (see on YouTube - very drastic!)
One of the most persistent myths about sleep is that our body is programmed to get as much sleep as possible. Even some reputable researchers subscribed to this idea! They compare sleep to overeating. Some note how long Inuit sleep in winter. Others note that people allowed to sleep freely often binge heavily clocking up an indecent number of sleep hours. As if conservation of energy was the main function of sleep. As if all animals were made as lazy as they are perpetually hungry. However, few can demonstrate any evolutionary or biological advantage to getting more sleep than neurally necessary. This harmful myth might make you think that free-running sleep will make you sleep longer in the same way as free access to the kitchen will make you overeat. Considering the known functions of sleep, there is no specific benefit to sleeping beyond the standard 6-8 hours. Sleep is a physiological consumer of benefits accumulated in waking (such as learning, exercise, etc.). Its healthy homeostatic regulation roughly ensures the optimum proportion of sleep to waking. People who binge on sleep in free-running conditions, usually come from a period of long-lasting sleep deprivation. Their sleeping time quickly drops to their natural average after a couple of days of the free schedule. If your main concern is time, you can survive on less sleep and get more time at the cost of your mental acuity. If your main concern is the brain power, you should live by the motto: Maximum efficiency of sleep is accomplished when sleeping without artificial sleep regulation (i.e. without alarm clocks, pills, designer schedules, etc.). Free-running sleep schedule will make you sleep less on average. It will make you sleep much less than on those days of any artificial sleep schedule that forces you to catch up with the accumulated sleep debt. Irregular schedule is bound to produce deficits because you can accomplish irregular sleep only by interfering with it.
With all the mail criticising my polyphasic sleep article, not a single one!, came against the basic scientific premise, which was supposed to make the core of my argument. I received some mail that quoted from scientific literature or from Dr Stampi's book. However, again, not a single one! came against the basic scientific premise (see the yellow inset below). To make the article readable, I mixed science with humor and a degree of provocation. My experience says that the importance of the message does not correlate with the degree of article's popularity. I never get any comments on "Two component model of memory". It does not affect anyone's emotion. It reads like dry science. We got very few reprint requests back at the day of publication (before placing the article on the web). And yet it might be one of the most important contributions of SuperMemo to understanding memory. This is why when writing the polyphasic sleep article, I chose a more provocative style to address the younger audience. Understandably, most of the criticism focused then on the "readable" portion (despite a large disclaimer that it should be taken with a grain of salt). As such, all criticism missed the main point of the article (!) and did not contribute much to the discourse. Here is a chance for the critics again to address the central point:
In practise this means that only mono- and bi-phasic sleep patterns are healthy and recommended. Note that the mono- vs. bi-phasic choice will depend on the circadian wave function, which has two minima in a 24 hour period, only one of which has been proven essential for the correct function of sleep (until now). Polyphasic entrainment is just a pipe dream. So is the even more extreme hope of sleep on demand. Please do not send me mail with Eureka exclamations that there are polyphasic women in this world, or that my blog selection is biased (because it is!). Unless you can provide evidence against the core argument in yellow above, our exchange is likely to be pointless.
Lots of critical mail mentioned my "hidden agenda". Ever since I wondered what my hidden agenda might be. Standard ulterior "agendas" revolve around money, feeling important, or a ticket to fame. The article is free, and earns me no money. It hardly mentions SuperMemo, so it does not serve as a promotion article. It earns me no fame. How about feeling important then? The article had some success in preventing some people from plunging into a polyphasic waste of time. Therefore I do consider the article important. Yet at 50% criticism rate, I would rather need to don a mantle of thick skin even though I am rather of fabric that loves loony criticism. The more awkward and preposterous the accusation, the more fun it is to combat it. Perhaps this mechanism breeds people who like to rub others the wrong way. Yet, if all I wanted to do is to be contrary, I could employ more aggressive and unkind tools of derision. I opted for the opposite: due respect to those young people who experiment with their health. I combined that respect with a bit of harmless fun poking for the sake of just making the article a bit more effective in addressing the emotion of the reader.
In addition to the original agenda behind the article, you may think that after 5 years, a new agenda might be emerging: it would not be nice to eat crow! Most of people hate to admit their mistake. However, this is less of a problem in science, where each opportunity to change one's mind is always associated with learning something new. True hard-core scientists love to find out they were wrong because they equate it with a major step to getting closer to revealing the truth. I am not too emotional about personal accomplishments or being always right. I would also rather welcome the need to admit being wrong because it could only be a result of some major scientific discovery. It would certainly require an update to our models of sleep. This would mean that we would better understand the mechanisms of sleep, and new knowledge always opens new vistas, esp. for my true core agenda: striving at faster and better learning! Unfortunately, the probability of such earth-shattering discoveries is not much greater than a chance that humans will soon find a way to squeeze through a wormhole.
Someone suggested that my agenda is "free running sleep". This is hard to understand. I do adhere to free running sleep religiously. I do tell people of its blessings (and inconveniences). However, other's people polyphasic sleep does not interfere with my free running sleep lifestyle. It does not detract from its value. It does not hurt me or shame me. Why would this be my agenda?
My true and only agenda behind writing the article was to stop young men from doing stupid things to their health. In the belief that polyphasic sleep is not feasible, I have no agenda: it is just a fact that needs to be told to some people.
Someone warned me that a foray into a pseudoscientific field, as well as battling superstitions with sarcasm or derision may undermine the stricter and more scientific feel of supermemo.com. This prediction seems to be wrong. Polyphasic sleep and SuperMemo audiences are largely separate. Most of people get to SuperMemo when they discover it when searching for efficient ways of learning. They already have a strong intuition that they need something like SuperMemo, and only need to find the right tool for their goals. They hardly ever decide upon it having read lengthy articles. And in those rare cases, they are predominantly encouraged. This probably comes from the fact that only one kind of people read supermemo.com: those who like science. No one with a true love for science can go pass by SuperMemo indifferent. The polyphasic article clearly warns when it moves from fact to humor (and intentional bias). I see no evidence it has hurt SuperMemo in any way. At the same time, I got some mail indicating that people who originally searched for polyphasic sleep articles became interested in SuperMemo. All in all, the article does not seem to have much impact on SuperMemo, and whatever impact it has, it is probably positive. Most of angry mail came from worshipers of polyphasic sleep, none of who, admitted ever using SuperMemo. No wonder. They are rarely of the science-loving type.
Some readers concluded that I might be a researcher who studies polyphasic sleep for a living. No! I took on the subject only as a short-term assignment. I study the impact of sleep on memory and learning. Even though all extreme angles taken to any subject in science are always a provocative source of inspiration, in the light of my interest in learning, polyphasic sleep emerges as an extremely dangerous lifestyle formula. Luckily, it is not sustainable enough to do much damage, however, it also helps perpetuate lots of catchy myths that may affect how young people approach sleep and health in general. Polyphasic sleep is not a neat study subject. Scientists like simplicity. They construct simple research models to make it easier to arrive at valid conclusions. I love free running sleep concept as a research model. It speaks of unadulterated natural healthy sleep. Polyphasic sleep was invented for unnatural survival situations, and its Uberman variant is a widely mutated invention of teenagers who hope to save time on sleep or solve their sleep problems. Choosing a polyphasic sleep as a model, would be like choosing a multiplanet system to test Newton/Keppler's laws, while a two-planet system would do as well and produce results eons earlier. Instead of complex Fourier analysis, we have simple and clear formulas that tell the entire story.
Someone accused me of using derision and painting polyphasic sleepers as dumb individuals who cannot figure out that polyphasic sleep is impossible and comparisons with da Vinci and Edison are simple myths and Internet rumors. This accusation can only come from inattentive or selective reading. Let me requote: Even though it is not nice to poke fun at anyone, I hope I do it for the right cause. After all, ignorance and mental flops happen to everyone, incl. the greatest geniuses of history. Those young men show many characteristics that will make them successful in life: perseverance, curiosity, willingness to experiment through pain, voracious attitude, zeal for action and change, etc. Many of those quoted bloggers will go on to do great things in life. Naturally, I do not believe that will happen on a polyphasic sleep schedule.
Nevertheless, with all the extra information available on the net today, it is true that it is less justifiable for a reasonable person to take on polyphasic sleep today than it was 5 years go. Polyphasic sleepers today are not dumb. However, they are at least very unscientific. They may also often be pretty narcissistic or downright arrogant. Those characteristics do not help clear reasoning either.
Is it possible that there are individual who can actually adapt to the polyphasic sleep despite its infeasibility for the majority of the population? This is possible, but highly unlikely.
I raised that possibility less for its probability, and more for the sake of softening the accusation that those who claim polyphasic sleep feats are liars. To make "mutant theory" workable, we would need a series of mutations that would produce sleep without a circadian component. Or a mutation that would allow of homeostatic generation of circadian states that periodically occur in the brains of all vertebrates. It is as hard as to imagine a mutation that would allow of defecating in 25g portions. Or a mutation allowing of asynchronous voluntary peristalsis. Or a mutation that would replace a blinking reflex with two separate independent regulatory blinking mechanisms for both eyes. Or a perpetual syncopated heart rhythm with alternating 3:6:3:9:3:6 interval ratios. Or a separate contraction of atria, or separate repolarization of ventricles, etc. Or a menstrual cycle that can be entrained to shift-work with bleeding every 9 days. Why do not people try those "physiological manipulations"? Actually they do. But it takes a hard-core looney to try to prove that "sleep is not necessary" or even "food is not necessary and can be substituted with meditation". The closest disorder that can match the hypothesis that polyphasic sleep might be enabled by a mutation is narcolepsy, in which individuals node off many times during the day indeed. However, this is a homeostatic disorder that does not flatten the circadian function. As such, narcoleptics sleep more than healthy people, not less.
I was delighted when the BBC turned to me to assist in designing an experiment in which a BBC presenter would attempt polyphasic sleep. However, program's limitations made it impossible to run the experiment on the proposed scientific basis with a supervision of a sleep lab. Nevertheless, the final outcome turned out pretty hilarious. The guinea pig volunteer turned out to be no one else than Bill Turnbull! The program ultimately aired in 2006 on BBC One's The One Show. Bill would present the Breakfast during the experiment, and the audience had an opportunity to see the impact of the experiment on his sleep-deprived performance. Unfortunately, the show did not make it to YouTube for your enjoyment.
Some of the criticism came from people who read Claudio Stampi's book Why We Nap. My article was accused of trying to contradict or undermine the contribution of a reputable sleep researcher. It is true that with the advantage of two extra decades of research, I disagree with some of Stampi's original hypotheses. Largely so does Stampi. Let me then unequivocally express my admiration for Stampi's passionate research and meticulous analysis of human reaction to drastic changes in the sleep schedule. His research can definitely be considered as pioneering work in the study of the extremes of chronobiology. For those who still believe that Stampi advocates polyphasic sleep as a lifestyle, an ancient quote from his book should clear things up: "the author would like to caution against misleading interpretations of these conclusions. What is being proposed here is not that polyphasic sleep is preferable to monophasic sleep, nor that everyone should now switch to a multiple napping behavior "panacea." It appears obvious that quasi-monophasic sleep — monophasic sleep plus occasional naps — is what comes most naturally to the majority of adult humans and a few other species. If somewhere in evolution such species have developed the ability to sustain wakefulness for relatively prolonged periods, most likely this ability occurred in response to some sort of important and advantageous adaptive pressure".
It is important to note here that Dr Stampi could identify only a modest decline in cognitive function during his polyphasic sleep experiments. This may stand in seeming contradiction with other research or with simple circadian measurements of memory performance (as in the circadian graph picture). Including a circadian component in measurements yields siginificant cognitive differences in the course of a normal undeprived waking day. The tests Stampi chose to measure cognitive performance skirt around the essential question as to the primary long-term neurophysiological function of optimally timed REM-NREM interplay in sleep (in Stampi experiement with Francesco Jost, REM and NREM rarely occurred together). If the hypothesized memory storage optimization function is considered, it is impossible to verify the status of memory with short-term tests as, in theory, the network function of the brain taken as a black box should remain unchanged. The neglect of sleep structure would show only as a cumulative long-term inability of the brain to build up new skills and reasoning powers. Secondly, the creative potential of an optimized storage is also difficult to measure, and will definitely show a cumulative effect requiring a long-term study. Last but not least, lack of the circadian effect can only testify to an insufficient sensitivity and/or timing of the tests chosen. Even if the homeostatic component of alertness ensures that we can seemingly focus on simple mental tasks and perform them pretty well (e.g. memory tasks, driving, simple calculations, etc.), the circadian low will affect the ability to sustain a mental effort or undermine its creative aspect. Tests that are sufficient for Dr Stampi's goals (e.g. maximizing alertness in a solo yachting race) cannot be used to make claims about the long-term impact of polyphasic sleep as a lifestyle. One polyphasic adept asked me: "I want my doctor to supervise my experiment. What parameters, do you think, he should track?". It is not much different than asking: "What tests I could do to check if smoking is safe? What tests can help me see the impact of smoking on health?". We all know that smoking or shift-work do not cause a significant impairment in a short term. In the long run though they both can kill.
It should also be noted here that even in serious sleep medicine literature there is a confusion between the homeostatic and circadian sleep components. Very often, researchers fail to differentiate between the two when investigating impact of environmental factors on sleep. We all know that coffee can help one survive a sleepy moment. It is important to ask though if its effects are homeostatic or circadian. Can coffee dispel sleep inertia? Can it help overcome circadian lows? It is not enough to say that coffee helps overcome sleepiness if its impact on the circadian sleepiness is negligible. Everyone who is familiar with the jet lag can testify that the foggy brain state does not evidently deprive one of one's basic mental skills, and yet it can entirely ruin one's productivity by affecting self control, creativity, motivation, and more. This is why globe-trotting politicians are a poor material for groundbreaking peace or trade deals, even if they believe they can function well on 3 hours of sleep or in a jetlagged condition. Dr Stampi's findings, highly applicable to emergency situations, should not be used to diminish the importance of well-timed natural sleep for the function of the brain, and the fact that artificial designer sleep schedules are very harmful.
In my article I wrote: Whoever claims to be on a perpetual polyphasic schedule must be either suffering from a sleep disorder, or be a liar, a mutant, or a person with a mulishly stubborn iron-will. Lots of critical mail pointed to the blog of Steve Pavlina who claims to have adapted well to polyphasic sleep. Pavlina might be the only notable case to make such a claim, and is used as an example to contradict the claims from my article again and again. Even though, in recent months, more claims of success surfaced on YouTube, Pavlina's loneliness in the success club resulted in more and more bloggers using his reports as a guideline to polyphasic adaptation. Without a detailed study of this single case or at least some communication with Pavlina himself, I cannot provide a definite reply, and can only voice my skepticism. The most likely interpretation might be that Pavlina survived his experiment through sheer will power (he is a motivational speaker that is unlikely to be short on this quality), however, in his blog he writes "My energy and alertness were excellent once I made it through the adaptation period". Someone suggested that he might be "blessed" with an adaptation mutation. This is the least likely interpretation. Any mutation to a healthy sleep control system is likely to put it out of kilter. Conceivably, polyphasic sleep might be a relief if the system lost some of its circadian periodicity, however, such a mutation would primarily manifest itself with a difficulty in obtaining a healthy sleep rhythm with a typical refreshing night sleep, which clearly is not the case with Pavlina. I can only suggest the reader gets in touch with Pavlina or skeptically read his blogs to draw his or her own conclusion. A word of caution though, Pavlina's blog is peppered with misleading inaccuracies. For example, he writes: "Adapting to polyphasic sleep is like changing any habit, such as quitting coffee. It may involve some force and struggle for a few days to break the old pattern, but afterwards your new direction feels perfectly normal, and no ongoing force is required. Day 2 was the struggle. After that it was all downhill". That "withdrawal" premise underlies the hopes of many polyphasic sleepers. However, coffee is an addictive substance and withdrawal is governed by the rules of addiction. Recovering from a jet lag is based on an entirely different mechanism of sleep phase shift. Finally, "adaptation" to polyphasic sleep is neither a case of "night sleep withdrawal" nor "night sleep phase adjustment". It is just an attempt to partition the circadian rhythm, which is biologically not possible. A degree of adaptation is achieved by the compression of sleep stages that make the schedule more bearable, however, true adaptation manifested by natural waking before the alarm is not possible!
Another case often asked about is that of Puredoxyk - the "inventor" of the "Uberman sleep schedule". Not the least for her being a woman, which immediately gets the dander up of the "polyphasic women lie" conspiracy theory circle. Again, without a detailed analysis of blogs and multiple new articles on the subject by Puredoxyk herself, I should not make speculative statements on her particular sleeping regime. However, what strikes me in Puredoxyk writings is that she instantly rings credible. Let's have a peek at what I will call the Puredoxyk Law:
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*.
* 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
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 blocks 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.
Naps = 5.6 - 0.8*CoreSleep
With this formula, the duration of naps will determine the break even point for the total time gain on polyphasic sleep. Obviously, that break even point will coincide with the situation in which the total amount of sleep is constant. After summing up nap time with sleep using the above formula, we can see that the total sleep time will depend on two variables: the number of naps and their duration. After differentiating for the number of naps, and comparing to zero, we arrive at the conclusion that the break even point stands at naps lasting 70 min. This corresponds with the total sleep time of 7 hours. This means that naps that last less than 70 min. will produce a net gain on the total amount of sleep in a polyphasic sleeper. It would be interesting to analyze irregular sleep logs that comply with the above law as they could answer some questions on the winner in the tug of war for sleep efficiency between the regulatory powers of the free running sleep and the adaptive powers of the sleep compression induced by alarm clock use in polyphasic sleep.
The net time gain in a short-nap regime, obviously does not translate to a brain gain, and this should not be understood as a recommendation to seek minimum total sleep time. I posed the above problem only as an interesting mathematical relationship, which provides a neat formula for the total sleep debt that might be of use in modeling sleep in conditions where sleep is terminated prematurely (e.g. with an alarm clock). Neither SleepChart nor SuperMemo account for sleep debt as both have been designed for the ideal free running sleep condition. Obviously, any form of sleep debt is unwelcome as it implies unfulfilled neural function of sleep. In short: Instead of aiming at minimizing the sleep time, we should aim at maximizing the brain effect of sleep.
That Puredoxyk got sufficient experience in sleeping polyphasically to formulate the above law without any specific logging tools indicates that she needed a pretty vast array of napping permutations to see the bigger picture, which in this case seems highly plausible. The Puredoxyk Law can be interpreted as a demonstration of how a healthy mono- or biphasic sleep can be stretched into a polyphasic phase space with an increasing degree of sleep debt. Puredoxyk herself calls her new sleeping regime that includes a "core nap" the 3-hour Everyman schedule. This schedule sounds pretty sustainable if it is not too heavy on the use of the alarm clock. After all, a third of Americans can function reasonably ok despite committing the neural crime of using the snooze button on a daily basis with the average use said to be around 3 times. Needless to say, this Everyman schedule stands as a pretty wide departure from the original Uberman formulation that I found particularly harmful.
In the past, I have received a number of sleep logs with pretty irregular sleep patterns (including multiple naps). Those logs were accompanied by some anecdotal evidence that seems to indicate that those irregular patterns are strongly correlated with some personality characteristics. I can be widely speculative here and say that those are pretty neurotic and yet quite creative types (excluding cases that could be attributed to the use of prescription drugs). If that was to be the case, those sleep patterns might not be too good for longevity, but even free-running sleep will fail to straighten them out. This indicates that there could be genetic factors involved here, and the "mutation hypothesis" is far more likely to explain a perpetual irregular pattern than a regular fresh&alert Uberman pattern (see Pavlina interpretation). I would even avoid the use of the word "mutation" here as those "personality genes" must be pretty widespread in the modern population. How can Puredoxyk's case be interpreted, I have no idea, but it does not seem to be too extreme in its uniqueness, and, as such it can be, probabilistically speaking, deemed credible.
- Good sleep, good learning, good life
- SleepChart: Formula for healthy sleep
- Sleep and learning timeline
- Polyphasic Sleep: Facts and Myths
- How to nap
If you are interested in chronobiology and how it affects the feasibility of the polyphasic sleep, read the following physiology insert.
In my original article I tried to mix science with pop science, as well as with anecdote and humor. Predictably, nearly all comments and criticism referred to the pop part, and no meaningful reply to the science argument landed in my Inbox. At the risk of having the science approach ignored entirely again, I hereby present a new angle at looking at the art of napping. Hopefully hard data collected with SleepChart and SuperMemo should back up the argument and add to its illustrative and explanatory power.
Have a peek at the following amazing picture obtained in recent months with the help of SuperMemo. The graph shows the powerfully biphasic nature of the human circadian cycle. The horizontal axis shows the circadian time, i.e. the time that elapses from phase 0, i.e. the predicted "end of the night" time. The prediction comes from the circadian model employed in SleepChart and SuperMemo, and is derived from the sleep log collected in SleepChart and/or SuperMemo. The pink line is the predicted alertness derived from the same sleep log data using the two-process model of sleep developed for the purpose of sleep optimization in SuperMemo (the model is inspired by similar work of Alexander A. Borbely and Peter Achermann). The alertness is a resultant of the status of the two sleep-drive processes: the homeostatic process and the circadian process. The blue dots are recall data taken from an actual learning process in SuperMemo. In other words: Pink is the model, blue is the data. Both tell the same story! For skeptics who do not believe in scientific models, blue-dot unprejudiced data should be the ultimate clinching argument. The graph tells you unequivocally that we got two major peaks of alertness during the day. More importantly (in our polyphasic sleep context), it also states clearly that there are only two valleys conducive for sleep and/or napping.
Myth #1 of polyphasic adaptation: a nap is a nap is a nap. Even though this myth is often unspoken, it lives deep in the psyche of polyphasic adepts who do not seem to realize the myriad of genetic, metabolic, neural, and hormonal processes that cycle through the human body throughout the roughly 24 hour period. Below, I include a general partitioning of the circadian cycle with a short analysis of what processes occur when a nap is taken at each selected point of the cycle. Naps taken at different points of the circadian cycles are as different as chalk from cheese. Some are refreshing. Some are a waste of time. Some may be unhealthy (or at least inefficient). Some will last several hours!
Myth #2 of polyphasic adaptation: the circadian cycle can be ignored or abolished, and the sleep can be reduced to one-dimensional homeostatic process. This myth is unspoken as well and definitely comes from the lack of understanding of the two-process nature of sleep. Some polyphasic adepts might be knowledgeable enough to have heard of ultradian rhythms, however, little do they realize the overwhelming power of the primary circadian sleep component (as seen in the graph above). Consequently, the myth bears a belief that naps can be induced at will at any time that is sufficiently far away from the prior nap.
My original "Polyphasic sleep for dummies" section was not very successful in conveying the power of two sleep processes in controlling the timing of sleep. Here is another approach from a different angle. Using the graph presented above, let's imagine what is happening when the nap is taken at different times of the circadian cycle:
Phase 0: Waking time: napping in Phase 0 is possible, and largely depends on the history of prior sleep (see 0 on the horizontal axis in the graph above). Phase 0 naps after a normal night sleep can be considered as a complement to the night sleep if it was not effective enough. Such naps consolidate with the night sleep in sleep models and are an efficient way of extending the night sleep in cases when it was interrupted (e.g. by noises, bursting bladder, health issues, etc.). Phase 0 naps after a sleepless nap can serve as an inefficient substitute for the night sleep. Such sleep will be short, unrefreshing and leave a sleep debt. It will also introduce unwelcome oscillations in the circadian system that may take a few days to clear up. Such sleep is often used by night-shift workers to get some mental boost for a day. It is still far better than no sleep at all. The rule is simple: if you are sleepy at Phase 0, nap at will. Your brain clearly needs more sleep.
Phase 3: Creativity time: napping in Phase 3 should not ever be possible in a healthy well-regulated system (see 3 on the horizontal axis in the graph above). Successful sleep at this time is an indication of sleep deprivation, poor quality sleep (e.g. due to sleep apnea), sleep in a wrong phase (e.g. taken too early), sleep disorder (e.g. narcolepsy), etc. This is probably the hardest time to nap of all. However, I am not aware of any bad effects of such naps for health or for sleep control systems.
Phase 5: Pre-siesta: napping in pre-siesta slot is possible. However, such naps are likely to be short and not as refreshing as Phase 8 naps. They are also more likely to be REM-rich for circadian reasons. Those early naps can probably be recommended to people who suffer from sleep-onset insomnia, and who still want to boost the second half of their day in terms of alertness and creativity.
Phase 8: Siesta: perfect time for napping. As it can be seen in the graph, this is the period when the mental performance is at its mid-day nadir. It is not true that the nadir is caused by a hefty lunch (even though meals have a big impact on sleep control). The nadir is a natural expression of the circadian wave in sleep control. This circadian low time comes at the roughly same clock time as the subjective night nadir at a roughly 12 hour shift (e.g. if the middle of your night falls at 3 am, naps at 3 pm could be most effective). This is well explained in "How to nap". Dr Stampi also praises the value of siesta. Its benefits have been confirmed by numerous studies. It has been practised for ages in many regions of the world. It will definitely trickle into the corporate world as human productivity becomes increasingly dependent on one's creative powers.
Phase 11: Evening: this is not a good time for napping. In a healthy cycle, napping might be hard to achieve or impossible. However, even a minor degree of sleep deprivation will produce a nap that might trigger the control mechanisms responsible for the full-night sleep. Late naps are likely to be rich in NREM sleep and rob your night sleep of the vital SWS component. Those naps can last far longer than siesta naps. They can make you groggy. Worst of all, they can compound insomnia. Unfortunately, this is a type of a nap that a huge proportion of students take! Forced to wake up at indecently early times for school, kids and students struggle semi-conscious through school hours with negligible progress in learning. Learning in such a state only magnifies the pretty universal hatred of school. Phase 11 nap is then the only way to survive the day and get some actual learning done in the evening. The body clock shifts the subjective night to the morning hours. The positive side effect is that evenings can be filled with effective studying. The negative side effect is that the student finds it impossible to fall asleep before 3-4 am, and welcomes the new bright school day with an alarm clock that rings in the middle of the subjective night. This perpetuates the cycle of suffering and school hate. Nobody has ever estimated the global consequences of this phenomenon that includes an impact on adolescent attitudes that are notoriously fraught with problems. Neither has anyone come up with a practical solution (shifting school hours usually results in kids "adapting" to the new cycle by shifting their bed time as well). I am not able to recommend a solution here either. Skipping evening naps might be better for the quality of night sleep and for the stabilization of the circadian cycle in the earlier phase, however, that would effectively rob those students of their only time in which they can learn. Those evening naps are also the only meager substitute for free-running sleep that those young brains crave. The only time when the brain gets what it wants. If I was to answer: to nap or not to nap, I would probably have to admit that evening napping is the lesser evil in a majority of cases.
Phase 14: Pre-sleep: this is a particularly bad time for napping. Initiating naps at this time should be relatively easy. However, pre-sleep naps are likely to produce one of the following unwelcome outcomes: long-nap-short-night or long-night-early-waking (depending on the current status of the sleep control system). A pre-sleep nap is likely to result in triggering the night sleep sequence. However, this sequence is not unbreakable, and can result in early awakening combined with the difficulty in launching back to sleep. This is particularly likely if the homeostatic sleep process generates substantial sleepiness while the circadian process is not yet mature for the night sleep. As a result, such a pre-sleep nap can yield less total sleep than a normal night sleep. This long-nap-short-night will not entirely fulfil the physiological function of sleep. Consequently, your alertness levels for the next day are likely to dip substantially. The less unfortunate outcome of a pre-sleep nap is if you successfully trigger the uninterrupted night sleep sequence. However, you will likely prematurely run out of the homeostatic process before the circadian function of sleep is completed. You will probably wake up earlier than usual. This is the long-night-early-waking outcome that produces nights that are amazingly unrefreshing considering the fact that premature sleep is often much longer than an ordinary night sleep. The reason for this low sleep efficiency is probably the scarcity of REM sleep which is strongly circadian. Moreover, for circadian reasons, your morning is likely to be unusually sleepy!
Phase 18-24: Night sleep: if you try to nap in Phase 18-24, you are bound to trigger a normal healthy night sleep. This is ok as long as you do not get down to "napping" with the evil intent of stopping the process in 20-40 min. Here is were the pain of polyphasic sleeping becomes hardest to bear. As Dr Stampi noticed two decades ago, it is not the problem with staying awake or with falling asleep that is most exasperating. The most painful part of a polyphasic life is when your brain wants to trigger the night sleep sequence and a polyphasic adept stubbornly disallows it! This is as bad an interruption as any other abrupt stop to an all-or-nothing physiological process (urination, defecation, orgasm, swallowing, heart beat, sneezing, coughing, childbirth, and the like). Many polyphasic bloggers note: "I noticed that when my naps get longer, I get groggy. So I try to keep them under 20 min". Duh! If you do not launch the night sleep sequence, you will not suffer the pain of interruption. Why nap in the first place then? It's easier to delay defecation than to stop it in the middle. The most unusual night-time nap control method I have encountered was... "I keep lots of junk in my bed. That keeps my naps short"!
Important! The two alertness valleys are biologically dissimilar! As it will be shown later, only the night-time valley can produce a typical long-drawn periodic NREM-REM interplay with a gradual increase in the proportion of REM. The subjective night period is marked by a characteristic increase in the release of melatonin. The length of siesta sleep, as shown below, in the biphasic sleep graph, is 4-20 times shorter than the natural night sleep. Phase response is elicited by stimuli that precede or follow the night sleep. However, the same stimuli my affect the timing of the siesta nap, which in turn may have an indirect impact on the cycle phase.
This section provides some data that fortify the view that polyphasic sleep is not entrainable. To follow this text you may need some basic understanding of chronobiology, SleepChart and SuperMemo.
Understanding the control mechanisms that produce sleep and wakefulness is extremely helpful in individuals suffering from a number of sleep disorders, in particular, insomnia and phase-shift disorders. Simple measurements of circadian variables and simple tools of chronotherapy may bring sound sleep to those who often struggled for years with insomnia, unsatisfying sleep, or sleep in wrong hours. Better understanding of chronobiology could also help extinguish dangerous practices such as poorly planned shift-work, disrespect for health consequences of the jet lag, cumulative sleep deprivation and the Internet fad of polyphasic sleep.
A few years ago, we have published a freeware application for charting sleep data and circadian graphs (see: SleepChart). SleepChart makes it easy to analyze a person's sleeping habits in terms of circadian timing, effects of wakefulness on phase shifts, homeostatic sleepiness, etc. In this short narrative, a few conclusions are drawn from the comparison of SleepChart data collected by healthy sleepers and sleepers attempting to adapt to polyphasic sleep schedules.
Courtesy of the numerous contributors who sent in their data, we can draw a number of interesting conclusions. The most compelling one is probably the confirmation of the hypothesis that we might be facing an epidemic of Delayed Sleep Phase Syndrome (DSPS) in younger generations, esp. among students and people employed in high-tech jobs. The epidemic is a result of an ever-growing discrepancy between the environment in which humans and their primate ancestors evolved over the last several million years, and the environment in which we live today with electric lighting, Internet, computers, TV, rat race, and 24-hour society. The increasing gap between lifestyles and biology leads many to seek radical solutions and take on drastic measures. A quick survey of those who attempted the dangerous polyphasic sleep experiment reveals an interesting truth. Although the wish to squeeze in more waking hours into a day is a very appealing concept on its own, most of the "experimenters" began their interest in polyphasic sleep as a result of troubles with achieving refreshing sleep.
Most of healthy individuals are either biphasic, "crypto-biphasic", or monophasic. In the presented graphs, tightly spaced cluster naps are merged for clarity of graphs using a heuristic algorithm employed in the SleepChart application. SleepChart was designed for free running sleep, and some readings may thus be distorted for other conditions. In particular, you cannot map circadian or homeostatic sleep components using just behavioral markers without the free-running sleep condition.
In the presented graphs, the blue line corresponds with the ability to initiate sleep at any given circadian time. It aligns well with the alertness graph presented earlier. It aligns well with both the learning data, as well as the two-process sleep model.
The red line corresponds with the ability to maintain sleep. It reveals what is not visible in the alertness graph shown earlier: siesta naps cannot last long and will always be subject to an early natural termination (low red line under the first blue peak). In contrast, the period of subjective night is the only time of day when sleep can and should last longest (usually no less than 4-5 hours). The red peak is the reason why polyphasic adepts crave for "core sleep", wake up groggy, and need heavy alarm artillery to wake up in this critical period.
Monophasic sleep graphs will often show small siesta-time peaks due to the fact that even the purest monophasic sleeper hits crisis days in which a postprandial nap brings a welcome relief. Due to its "crisis nature", such nap may last longer than it is the case in a typical biphasic sleeper. This is particularly visible in irregular sleepers who show less discipline in sheltering their natural regular sleep hours.
In free-running sleep of an irregular sleeper or in cases of DSPS, we can see the impact of nighttime on the ability to initiate and maintain sleep. Independent of the innate circadian cycle, light has a powerful impact on sleep. In particular, its phase-shifting capacity will always ensure that humans naturally gravitate towards sleeping at nighttime. Only the advent of lifestyle that involves electricity and 24h work cycles triggered the present epidemic of sleep disorders, which indirectly contributed to the appeal of concepts like "Uberman sleep".
The above graphs with the horizontal axis taken as the time from waking can also be interpreted as a phase space. It can be demonstrated that no trajectory in the phase space will lead to an entrained polyphasic sleep. When alarm clock and/or sleep delay are introduced into the system, it may become chaotic. However, in free running mode, in quickly stabilizes around a roughly biphasic rhythm, often with a degree of phase-shift dependent on the lifestyle (primarily: interaction with zeitgebers and timing of stimuli affecting the endocrine system). The timing of phase-shifting, excitatory and inhibitory stimuli, even if they are repetitive and regular, may still lead to a degree of chaos in the system. This occurs if the period of their cycles is different from the period of the entrained circadian rhythm.
After publishing "Polyphasic sleep: Facts and Myths" a few dozen young men wrote to me requesting assistance in entraining polyphasic schedule. Ethically, I could not proceed in any other way but from starting to attempt to dissuade the young enthusiasts from proceeding with their polyphasic experiment. Needless to say, these are not the types that are easily persuaded to veer off their way. As I wrote previously, these are "rebellious men ready to seek new ways for maximum productivity". No scientific argument can be persuasive in such cases. After all, all reasoning can easily be quashed with "science does not yet have all the answers". None of the young rebels succeeded in entraining polyphasic sleep, yet some were persistent enough to provide some SleepChart data that sheds some more light on the implausibility of this sleep schedule.
In data obtained by Stampi one can see the forbidden zone in the first part of the day and clear homeostatic preference for the hours 15-24 of the waking day. The circadian curve is meaningless due to the fact that sleep is artificially interrupted. However, it would likely align with the blue sleep initiation curve (sleep initiation is easier and will preferably come in low circadian zone corresponding with the subjective night).
The picture shows the three most disciplined Uberman attempts I managed to collect from Greg (A), Bryan (B) and Claudiu (C).
At 9 days, Greg's attempt lasted longest and was quashed by the clustering of "core" sleep in the early morning hours towards the end of the experiment.
At nearly 5 full days, Claudiu's attempt was the longest "pure Uberman" before experiencing his first lapse into an extra nap. It is equally notable for its never having missed a single nap beyond Day 1. It is important to note, however, that many nappers find it difficult to determine if they actually fell asleep during naps that come in forbidden zones. What they mark as a nap might have actually been a few short moments of microsleep.
Last but not least, Bryan's attempt was still underway when I closed the period for data submission for this article. If he succeeded beyond the presented period, I will still try to update his case via an appendix to this article.
The data collected from Greg, Bryan and Claudiu can now be fed to SleepChart or SuperMemo to apply the two-process model that makes it possible to predict alertness on the basis of the history of sleep (to inspect your own data in SuperMemo 2008 use Tools : Timeline, choose File : Import SleepChart file, and use Shift+click on your sleep log to inspect sleep propensity at the chosen moments of time in the sleep log).
In the presented graph, the thick red line represents estimated alertness (computed using the same model as in the biphasic sleep graph). It is easy to see that its shape depends on the circadian phase at which naps occur (the circadian sleep propensity is marked in light blue). The graphs were juxtaposed so that to align nap timing while having them occur at different circadian phases that produce different alertness profiles.
Even though the sleep model used in SleepChart/SuperMemo applies to free running sleep, the symmetry of Uberman napping nullifies the need to correctly predict the circadian peaks and valleys (wherever the peaks occur, they will largely intersect with the nap grid at random). In addition, if regular sleep data are collected before the polyphasic sleep experiment, correct subjective night estimations from that period will carry over across the first few days of the polyphasic experiment. After all, only phase shifts can position the wave phase. The same mechanisms that makes polyphasic sleeping so hard, can also be used to explain it with the model designed to serve free running sleep condition.
What primarily emerges from the graphs presented above is the typical "rollercoaster effect" of the "Uberman sleep". Unlike a typical sleeper who wakes up refreshed and goes to sleep tired, a polyphasic sleeper will experience moments of extreme euphoria (e.g. at 4 am in the middle graph), and discouraging downers (e.g. 15:00 in the bottom graph). The presented alertness estimates correlate well with the subjective "focus and motivation" assessments made by the sleepers themselves. In the bottom graph, where a nap at 23:00 produced a major surge in alertness, the nap at 3 am delivered nearly nothing. This produces a typical rollercoaster of enthusiasm and self-doubt in a polyphasic sleeper. After short naps that occur at the minima of circadian sleep propensity, a polyphasic sleeper may reach heights that are not known to ordinary sleepers. Those surges of enthusiasm verging on euphoria are pretty unique due to the fact that an ordinary sleeper nearly never naps at circadian sleep propensity minima. Those moments can make a polyphasic experimenter update the blog with "never felt better - creativity at its maximum". At the same time, some naps can only make things worse. For example, the nap at 3 pm in the bottom graph taken on June 23 does not seem to produce any boost in alertness. It was then followed by an hour long "correction" that would not boost alertness either. Moreover, the cresting circadian wave will produce the unpleasant feeling of grogginess (i.e. sleep inertia) that should be familiar to shift-workers. That combination of sleep process variables is also responsible for the foggy head of the jet lag. This illustrates what Stampi noticed in his experiments that it is not hard to stay awake on a polyphasic sleep. The hardest thing is to wake up from naps that occur at the circadian crest.
In the presented example, a polyphasic adept started with 4 naps of 30 min, and a "core sleep" of 3 hours at 20:00 with an intent to reduce it to 30 min overtime. However, the adept kept failing to fall asleep during some naps and continued to struggle with alertness in some waking slots. The core sleep could not be shortened without further sleep deprivation. Instead, the core sleep increased in length slightly and moved to a later hour. Gradually, daytime naps started disappearing until the adept moved to a typical biphasic sleep of 5-6 h in the evening, with a 30-60 min. nap in the morning (and an occasional extra nap during the day if the core sleep resulted in heavy sleep deprivation). One year later the adept is nearly monophasic with only one rule leftover, "try to go to sleep before midnight".
SleepChart implements a concept of the Recursive Phase Response Curve (rPRC). The curve is recursive because it is first obtained by computing the impact of phase shifts in sleep blocks in relation to the middle of the subjective night line computed using statistical methods. Once the first approximation of rPRC is obtained, it can be used to produce a better approximation of the middle of the subjective night line that is then used to generate a better approximation of the rPRC. A few iterations of such a process are sufficient to produce the best fit of the rPRC that corresponds well with the actual sleep data (SuperMemo uses a fixed rPRC that roughly corresponds with rPRCs obtained with SleepChart). Whereas a typical PRC employed in chronobiology maps the response of the sleep system to a single stimulus (e.g. light, exercise, melatonin, or various chemical agents), rPRC is the resultant of all natural sleep delaying factors (incl. light, activity, stress, etc.). It can also be interpreted as a PRC, in which the waking activity forms the input to the free-running sleep system. Unlike a PRC which responds to a shifting factor, rPRC responds to the evening phase shift caused by the same factor. As such, rPRC is not a de facto PRC, and all departures from the free running condition invalidate the computation. The main advantage of rPRC is that it can be derived from sleep data without collecting blood samples, saliva samples or taking core body temperature measurements. This way, SuperMemo can correlate learning with sleep models that use only plain sleep log data as input.
In the presented graphs, Sleep delay (h) stands for retirement delay and equals the difference between the actual retirement hour and the optimum retirement hour as computed by SleepChart from the prior history of sleep. As the measurements refer to free-running sleep, no phase advance data is available due to the natural way of waking. The causes of sleep delay may include light, social interaction, stress, a conscious decision to delay sleep, exercise, ingestion of caffeine, ingestion of alcohol, medication, etc.
Phase shift (h) stands for a phase shift and equals the difference between two exponentially weighted waking hour averages on two successive days: the day on which the retirement delay occurred and the following day. Instead of the retirement hours, waking hours were compared as these are less affected by the homeostatic shift caused by the actual delay thus representing a truer reflection of the actual phase shift.
The flattening of the curve (as compared with a typical PRC) is caused by the recursive reference to actual sleep block data, which results from the fact that plotting the circadian low by SleepChart is an approximation based on the same sleep block measurements. As a result, polynomial approximation shows a slight increase in phase shift with increasing delay, which is not the case in typical PRC plots. The deviation of the retirement hour from the optimum retirement time may result from either environmental delay factors or from the approximation error resulting from heuristic procedures used to plot the circadian function, while sleep onset usually occurs naturally at optimum physiological time. The inherent asymmetry of the graph comes from the fact that earlier retirement is nearly always natural, while delayed retirement might be natural or forced (i.e. resulting from delay factors).
The graph presented below implies that in this particular case, delaying sleep by four hours results in a shift of sleep phase equal to 1.4 hours (which seems to be close the the maximum shift possible). Phase advance would require a natural onset of sleep that preceded the optimum retirement time by as much as 6 hours. Retirement at optimum hour results in the natural daily delay, in this particular case 1.0 hour, typical of DSPS disorders or conditions of isolation from zeitgebers (e.g. constant lighting).
It is possible to feed SleepChart with data obtained from "Uberman experiments". Obviously, the mere departure from free-running condition makes the outcome hard to interpret. Even the recursive nature of the procedure used to obtain rPRC cannot effectively cope with the lack of the leading circadian crest. With all that in mind, it is still interesting to peek at "Uberman rPRC" as it nicely reflects the chaotic nature of the sleep system subjected to a polyphasic experiment.
A polyphasic sleeper pushes his sleep phase back and forth largely at random. That can only result in a chaos and complete asynchrony of all neural, endocrinal and biochemical processes depending on the circadian component of the sleep cycle. One might expect serious health consequences of such a chaotic input to the system; however, natural defense mechanisms make life quite miserable for those who attempt a struggle against the natural sleep cycle. As a result, those who attempt polyphasic sleep are doomed to drop out sooner or later. There is, however, some hard-to-estimate risk of long-term impact of a "polyphasic experiment". This, in the order of decreasing likelihood, could include:
- desensitization to signals sent by the sleep control system
- long-term instability in the sleep control system
- damage to nerve cells involved in the control of the circadian cycle
The first possibility can actually be observed in shift-workers and people running a constant battle with sleep deprivation. In those individuals, the concept of "refreshed mind" and "refreshing sleep" becomes hazy, and one can observe an increased tolerance to permanent degree of tiredness coming from insufficient sleep or sleep in a wrong circadian phase. In other words, a degree of fatigue becomes a norm.
Instability of the sleep control system is also observed in shift-workers. It is not clear if shift-induced instabilities can become chronic or are fully reversible in a relatively short time. Even in a perfectly tuned sleep control system, minor rhythm perturbations, such as a switch to the DST, can produce regulatory ripples lasting for days. Larger perturbations might, in theory, result in uncoupling of master and slave oscillators with a particularly slow return to fully stabilized control. Perhaps this kind of uncoupling is the primary factor that underlies a myriad of disorders that plague shift-workers in the long-term.
Circadian wave function is like an electrocardiogram: if you try to become polyphasic, it is as if you wanted to change your heart rhythm and produce a separate contraction of right and left atria, or separate repolarization of left and right ventricles, etc. Your healthy ECG will always show the same regular pattern. You can phase shift your sleep as much as you can speed up your heart with exercise. Yet you cannot abolish the primary circadian rhythm as much as you cannot abolish