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Can someone point me to an argument or evidence supporting the suggestion that short polyphasic sleep allows most people to decrease their sleep requirements without negative cognitive, physical, or health consequences?
I'm a long sleeper (my sleep requirements are on the higher side), and I am interested in reducing my sleep requirements. I encountered the idea of polyphasic sleep after learning quite a bit about sleep. Polyphasic sleep is often touted as a way to decrease sleep need, via making your body quickly go into REM sleep. Quickly going into REM when asleep is a sign of either narcolepsy or sleep deprivation, neither of which are regarded as good things. I haven't found the original source for the idea that your brain goes into REM immediately on a short polyphasic schedule, but Claudio Stampi's studies suggest this is false. More recently I've seen some short polyphasic sleepers suggest the schedule will allow you to skip over the lighter stages of sleep so you can sleep more efficiently. With this much confusion and misinformation, I'm not confident about the justification for short polyphasic sleep.
The closest I could find to good evidence was the book Why We Nap by Claudio Stampi, which I have not read. gwern has suggested the evidence this book presents is weak, and others have noted that a more conventional idea (sleep until you are no longer tired) worked best in his studies.. Skeptics Stack Exchange has a question about polyphasic sleep, but it doesn't have any clear evidence that it works. There also are a few responses to Piotr Wozniak's article on the implausibility of polyphasic sleep. Neither of these responses seem to make many clear positive assertions about the benefits of short polyphasic sleep. In the latter response, a commenter suggested "polyphasic sleeping can be thought of as carefully managed sleep deprivation", which doesn't strike me a good thing.
Some folks (e.g., puredoxyk) have suggested that you have to deny that some people seem to work okay on short polyphasic schedules (or believe they are lying) to suggest that it doesn't work as described. I don't think so. It seems that the fraction of people who seem to do well on short polyphasic sleep schedules is comparable to the fraction of people who are short sleepers. I don't have any hard numbers for the former, but I believe it is on the order of 5% or so (puredoxyk suggested over 90% of attempts at short polyphasic sleep fail). The latter is more well studied. A fairly recent review stated that about 4.0% of people sleep less than 5.5 hours per night. So, my hypothesis is that those who do well on short polyphasic sleep schedules are short sleepers, and thus it doesn't make sense to suggest polyphasic sleep as a way to reduce sleep requirements.
Still, with so many rationalists buying into the idea, I'm wondering if I am missing something. I would appreciate any suggested reading on the topic.
But only people with excessive daytime sleepiness are tested for quickly going into REM, so the fact that they do doesn't tell so much. Anecdotally, I find that people with narcolepsy went quickly into REM before they developed the excessive daytime sleepiness. They seem to function quite well, until they develop full-blown narcolepsy. So I don't think it is reasonable to associate quick REM with narcolepsy. Sleep deprivation is another matter.