The Sleep We Need
We spend about a third of our life sleeping. It helps us restore our physical and mental capacity. We are ready for the next day after a full night of sleep but are dead tired when we only sleep a few hours. This article explores the why? how much? and other questions about sleep. Not only normal sleep cycles but also polyphasic sleep is explored.
What is Sleep
Sleep is the absence of consciousness, relative suspended sensory activity and inactivity of nearly all voluntary muscles. The body is at most time inactive and conserves about 10-15% energy during sleep. This number may strike people as low, and the reasons for sleep are still relatively unexplained. From the ecological perspective, it can be said that sleep could have had three ways or reasons of evolving; conserving energy, foraging (which predators do less, and sleep more), and predator avoidance (thus sleeping less). Some animals have found a way to even sleep with one side of the brain and not the other (unilateral sleep).
During sleep itself, the brain goes through four distinct phases. The first is Non-Rapid Eye Movement (NREM) stage 1 in which a person is falling asleep and the eyes open and close sometimes. In NREM stage 2 alpha waves from phase 1 are interrupted by sleep spindles and K-complexes (which help with tranquillity). Stage 3 NREM sleep is the slow-wave sleep, you are in a deep state of sleep and delta waves are the most active. During sleep, you mostly go through these phases first and from NREM 3 you go back to NREM 1 and finally REM sleep. Here most muscles are paralyzed, but at the same time, your brain activity looks alike to that of when you are awake. REM sleep deficiency is linked to a lack of learning complex tasks.
How Much Do We Need
How many hours a night do we need to fulfil the required amount of (REM) sleep each night? We experience about 90-120 minutes of REM sleep each night, with more REM sleep at the end of the night. A general consensus states that we need between 7 and 9 hours of sleep each night. This, however, differs between people, their physical activities and living habits. When you exercise more, the body takes a part of the sleep time to restore the muscles and rebuild them stronger than before. Most people take the required amounts of sleep in one go, but there are other ways too.
The most well-known of other sleep schedules is the siesta. People who take a nap every afternoon have a 37% reduction in coronary mortality. It also reduces the amount of sleep needed at night and reduces the total amount of sleep by 0,5-1 hour every day. Some more extreme forms of polyphasic sleep schedules are also around. One is called the Everyman and consists of 4,5 hours of sleep and two 20 minute power naps. Although a significant amount of waking time is gained, questions can be asked about gained productivity and loss of essential REM sleep. Sufficient research has yet to be done. This is also true for the Uberman schedule in which a person sleeps only 20 minutes every 4 hours.
I have some personal experience with Everyman (somewhere in 2010-ish). It enables for a lot of work (or gaming) to be done during the late night. The feeling of sleeping less also has an empowering aspect to it. The huge downfall, however, is social life, trying to nap between 4 and 6 PM every day is quite the task. But when challenged with a big workload, a daily opportunity for naps and the discipline of sleeping and waking on time, it is very possible to follow the Everyman schedule.
I can conclude that everyone needs an appropriate amount of sleep time. In still somewhat unexplained ways the body and the mind restore during the nighttime and allow you to function yet another day. Adopting another schema for sleeping can have some advantages of longer waking time. But be sure to spend them during something that requires attention, or you might fall asleep!
References & Further Reading: