Polyphasic sleep is a strategy employed by some people who want to spend more time awake. The aim is to have several shorter sleep periods throughout the 24-hour day, rather than one 8-hour sleep period through the night. Advocates claim that this allows the practitioner to sleep less total time, and therefore have more time for waking activities. The idea is that with more waking time, the person will be able to accomplish more productive work.
A prime example of "body hacking", polyphasic sleep does not occur naturally in large populations. People don’t normally sleep this way. Anecdotal evidence suggests most practitioners are men in their 20s and 30s who imagine they are geniuses or want to identify with geniuses who have reportedly followed this practice. Anecdotal evidence also suggests that most people who try polyphasic sleep give up on it within a few months.
Enthusiasts believe that while ordinary sleep consists of many cycles, much of the sleep period is wasted time, and REM sleep is the most important. It is believed that after being deprived of sleep during an adjustment period, the brain will start to enter the Stage 3 (deep sleep) and REM sleep much quicker - with the result that each short nap contains almost solely of such sleep.
It used to be thought that REM is the main reason we sleep and that REM is largely responsible for the mental rejuvenation effects. Scientists no longer believe this and now recognize that light sleep, deep sleep, and REM are all important.
There is not much scientific evidence to support the polyphasic sleep theory. Sleep researchers do not investigate this practice, and medical professionals, including sleep specialists, do not recommend this technique. Everything we know about sleep suggests it is a sketchy idea, although it is unlikely to harm anyone so long as the practitioners do not drive or operate heavy machinery while sleepy.
How does polyphasic sleep differ from fragmented sleep? It’s largely a matter of degree and intent. Fragmented sleep is considered undesirable. Polyphasic sleep is something some people strive for. Fragmented sleep is typically marked by total sleep mostly concentrated during the nighttime hours, with short interludes of waking. The fragmented sleeper is often sleepy during the day, while the polyphasic sleeper (if it works as planned) is not sleepy.
People stuck in extraordinary circumstances sometimes use polyphasic sleep if they cannot afford to be sleeping for long periods. For instance, open-ocean yacht racers use this technique. Astronauts in space missions and military personnel in certain endurance training regimens follow polyphasic sleep regimens.
Another name for this pattern is Dymaxion Sleep, which came from polymath Buckminster Fuller who applied the adjective Dymaxion in many of his projects (The term Dymaxion comes from dynamic, maximum, and tension), . Others use the term Segmented Sleep.
Humans typically (normal pattern) get their daily sleep in one long stetch (go to bed at night; get up in the morning) or a biphasic pattern (dividing sleep into two halfs, separated by an hour or two of waking in the middle of the night). Some animals follow polyphasic sleep patterns or at least a more fragmented pattern than humans. This pattern may have evolved in an attempt to remain vigilant against predators. Anthropolical study of modern hunter-gatherer peoples suggests they sleep in an irregular pattern. While this is not a polyphasic pattern, one researcher told Scientific American that the hunter-gatherers experience find "sleep is a very fluid state." Reports of widespread polyphasic sleep in the wild are rare. People try to adopt this method, but it is not clear how.
However, different people vary widely in their sleep needs, and there are stories of geniuses such as Leonardo Da Vince and Thomas Edison sleeping in a polyphasic pattern. Buckminster Fuller reportedly slept only 30 minutes every 6 hours, or a total of 2 hours per day. This has doubtlessly inspired others into thinking they can increase their productivity by employing polyphasic sleep. This type of sleep pattern is even called an Uberman's sleep schedule – Uberman being the German word for Over-Man or Super-Man. Whether people are motivated to try polyphasic sleep because they suspect they are undiscovered geniuses or because they want to be more like those extraordinary individuals is unclear.
Is polyphasic sleep the same as Irregular Sleep Wake Rhythm Disorder? The difference seems to be one primarily of intentionality. ISWRD is a "disorder" and considered undesirable or at least a nuisance. Polyphasic sleep is "body hacking" by people who want to sleep in that manner.