Nowadays it is so regularly preached that we should get 8 hours of solid sleep that you could easily be mistaken for thinking this has always been the case. In fact, both the amount and pattern of sleep is affected by our genetic makeup, age and cultural norms. 8 hours is just the recommended amount for an average adult, with some adults requiring more sleep and some significantly less.
Cultural norms for sleep vary in different places around the world and have also evolved over time. Sleep in humans has polyphasic origins, meaning that we used to sleep several times in a 24 hour day. There have been numerous references found to a first and second sleep before the late 17th Century, when things started to change and more people started having one long sleep instead. One theory is that advances in lighting may have meant people stayed up later but to fit their sleep in, they started taking it in one long session. This single period of sleep each night has now become the cultural norm in many countries around the world.
Some cultures do still have polyphasic sleep patterns though. In Spain, afternoon siestas that last up to a couple of hours are still common. These have two purposes, to avoid the hot afternoon sun and to rest when energy is naturally low. Studies into the long term health benefits of siestas are mixed, with some showing benefits.
For the maximum benefit from sleep, it is important for it to not only be for the correct length but also at the right time. The main phase of sleep should coincide with the body temperature cooling as part of the circadian rhythm.
The purpose of sleep has been the topic of considerable discussion and research over time. Even today, the purposes and extent of the benefits is only partially understood. It is thought that sleep started off with one function and evolved to take on multiple purposes. The purposes of sleep now include restoration and healing of the body, processing cognitive memories and potentially staying out of harms way during the most dangerous period of the day.
Lack of sleep has been linked with lower cognitive functioning levels and, in the long term, an increase in a number of illnesses. Whilst we do not fully understand all the purposes of sleep, it is clear that it is of vital importance and should not be neglected.
Jen Blue has a degree on Psychology and specialises in writing about sleep and sleep apnoea. For more information about Sleep Apnoea visit www.devilbisshc.com/patient_
information .