In the early 1990s it was noticed in an experiment that when subjects were plunged into darkness for 14 hours they reverted to two phases of sleep. The first one of 4 hours followed by a waking period of 1 to 2 hours, followed by another session of 4 hours. This was seen by many as a natural rhythm. Evidence from a variety of sources throughout history has also mentioned the idea of there being two sleeping patterns, the first sleep followed by the second, with an ‘intermission’ between. Some have interpreted this as being an example of polyphasic sleep, and have experimented with other sleeping patterns throughout the day. But is the previous illustration an example of polyphasic sleep? Two things are noticeable in the original experiment. First the subjects developed a pattern of 8 hours sleep, and secondly the interval between lasted 1 to 2 hours and not a full days work. Polyphasic sleep seems to be superior only under specific short term conditions, that is, during periods of sleep deprivation. If you are only able to achieve 3 hours of sleep it is better to get 3 hours through taking short naps throughout the day rather than one long 3 hours of sleep. But this pattern is only sustainable for a short period.
In the above experiment there was a wakeful period of 1 to 2 hours. I wonder what difference it would make to someone who often awakens during the night to be told that this may be a natural rhythm rather than an example of insomnia. Nothing prevents sleep more than the worry about not getting enough. Often when someone awakes they stay in bed worrying about getting off to sleep again, thus preventing the very thing that they desire the most. Getting up for a short period may be more beneficial. But getting up to do what? a new term has entered the sleep vocabulary, that of, ‘sleep hygiene’. If you find yourself getting up and then unable to return to sleep it is worth considering whether the activity one has just engaged is has been beneficial or has been counterproductive. An obvious example would be drinking coffee. Coffee raises cortisol levels which are associated with levels of alertness. Cortisol levels during the night are naturally at their lowest. Stress also raises cortisol levels, so attempting to catch up on work would probably result in keeping one awake rather than aiding one to return to that second sleep. During the day cortisol levels slowly fall, with there being a particular dips around midday, early afternoon. Eating around this time helps to raise energy levels, also in many countries this has been associated with a time of partaking in a siesta. The siesta however is not an example of polyphasic sleep. If one finds that this is a period of extreme fatigue then it is more of a reflection of lack of sleep during the night. There is much talk about the idea of what is important is not the quantity of sleep but the quality, with too much sleep being as detrimental as too little. While this seems obvious, what is also apparent is that one does not go from wakefulness to deep sleep instantaneously, and the quantity needed reflects this. Sleep deprivation effects levels of alertness and quality of performance, as well as decreasing levels of positive mood. Sleeping patterns that follow the natural circadian rhythms of the body, which will have individual variations, will be more beneficial for long term health.