The Stages of Sleep
The study of sleep is a growing science. Human knowledge of the mechanics of sleep is relatively new. Until recently, most of the research has been in sleep disorders and related issues. It was discovered that there are several stages of sleep. Each of them has an important function in the overall process.
The information that follows is a very basic outline of these stages and their part in the sleep process.
Stages 1 and 2 are transitory states
In these states the body and mind are in the process of shutting down for sleep and then moving into the deeper stages. This is sometimes experienced as a sort of drifty feeling as you begin to fall asleep. In these stages, a person is easily awakened by noise, comfort issues, temperature, or other environmental issues.
When a sleeper is tossing and turning in their sleep they will typically rise back up to these stages of sleep. When this happens in the middle of the night, and there are issues of noise etc. the sleeper may become fully awake and conscious.
Any period of wakefulness less than 90 seconds is considered a micro arousal. Too many micro arousals each night can be a serious sleep impediment, potentially leading other more serious sleep issues.
Stages 3 and 4 are deep sleep stages.
In these stages the body is beginning the maintenance required by the body.
Hormones are released to aid in healing, relieving pain, and many other functions. This is the restful part the sleep process that has great benefit in alertness and energy levels.
Rapid Eye Movement sleep is the deepest level of sleep. This stage is where the mind begins to dream. Hormones are released that effectively paralyzes the sleeper, thus preventing movement and acting out the dream.
There is a sleep disorder called a REM state disorder where the body fails to produce this hormone. This can result in sleep walking, even climbing out of windows. This can be a very serious condition.
REM state is also the stage of sleep that memory is refreshed and stored. Getting the proper amount of REM sleep is critical to maintain mental sharpness, and functional memory.
Sleep patterns are defined as the rhythm of sleep. This pattern runs in cycles that are about one and half hours long in total.
The typical sleeper would have 5 cycles in a full 8 hour sleep schedule. The first sleep cycle of the night will include the 15-20 minutes required to move into stage two sleep, then longer periods in stages 2, 3, and 4. In the first sleep cycle there may only be 5 minutes of REM sleep. As the night moves on the pattern will change to include more REM sleep.
The fifth cycle will have about 40 percent of the total REM sleep in any given night. As you can see, the last sleep cycle of the night contains more of the critical REM sleep than any other.
A habitual 6 hour sleeper is getting only 4 cycles per night and is therefore missing a substantial percentage of the REM sleep needed to function at full capacity.