Sleep has been scientifically proven to be a dynamic process in which the brain continues to be active while we sleep. Sleep allows us to essentially maintain regular levels of cognitive skills such as memory, creative thinking, perception, motor skills and language skills. There are 5 separate stages of sleep that make up the sleep cycle.
Stage 1: This is the beginning of the sleep cycle which can be considered as the transition phase where a person transitions between a state of light sleep and wakefulness. Muscles begin to relax and the person starts to close their eyes in preparation for next stage of sleep. Generally speaking, the healthier a person is, the less time they will spend in this stage of sleep. Factors like sleep disorders can account for a person spending more time in this stage of the sleep cycle. This stage of sleep is very light and a person can still be easily awakened at this stage. Eye movement also slows.
Stage 2: In this stage, a person’s breathing pattern and heart rate slows and body temperature decreases, prompting the person into deeper relaxation. This stage of sleep takes up 45-55% of total amount of sleep. Brain activity slows with occasional rapid bursts of “sleep spindles” or rhythmic brain activity. Most adults will spend most of their sleep in this stage of the sleep cycle.
Stage 3: The brain begins to generate slow delta waves in this stage as the body falls into a transition phase between light and deep sleep. Breathing and heart rate become slow and steady and the body is very relaxed at this stage. About 3-8% of total sleep time is occupied in this stage of sleep.
Stage 4: Slow delta brain waves characterise stage 4 of the sleep cycle. A person goes into deep sleep also known as “delta” sleep. It is during this stage that repair, replenishment and restorative work takes place in the body. It is difficult to wake someone up in this deep stage of sleep. Disorientation may occur if a person is somehow woken up at this stage. Some people may even experience sleep walking at this stage.
Stage 5: The final stage of sleep is also known as REM (Rapid Eye Movement). Most dreams occur in this stage of the sleep cycle where brain activity, rate of respiration and eye movement increases. Although, heat rate and respiration are accelerated the body is immobile in this state. Due to the immobility of the body in this stage of the sleep cycle, it is considered to be the most relaxing stage. Science has not fully understood REM sleep, although 20% of our sleep is spent in this stage. It has also been shown that dreams which occur in REM sleep are beneficial to a person’s long-term memories.
A person goes through a complete sleep cycle from stages 1 to 5 which takes anything from 90 minutes to 110 minutes. It is important that a person experiences uninterrupted sleep cycles every night to wake up feeling rejuvenated the next day.