Before I discuss specific sleeping disorders and problems in this blog, I feel it is important to understand the stages of sleep.
There are five stages of sleep: stage 1, stage 2, stage 3, stage 4, and REM (rapid eye movement), which is probably what most individuals are most familiar with. During the time you sleep, your body cycles through each of the stages several times.
Stage 1: In stage 1 sleep, an individual begins to lose conscious awareness. Some people may experience certain types of hallucinations in this stage of sleep, which are known as hypnagogic hallucinations.
Stage 2: In stage 2 sleep, conscious awareness is lost.
Stage 3: Stage 3 sleep constitutes the beginning of deep sleep. It is in this stage that sleepwalking, bed wetting, and night terrors occur.
Stage 4: Stage 4 sleep is a continuation of stage 3 sleep. Stage 4 sleep is also deep sleep.
It appears that muscle and bone are built, the immune system is strengthened, and tissue is regenerated during deep sleep.
REM: In individuals who do not suffer from sleeping disorders, breathing and heart rate increase in speed and eyes move around rapidly (hence the term Rapid Eye Movement for this stage of sleep). Most of a person's memorable dreams occur in REM sleep.
Infants and children may spend up to 50% of their sleeping time in REM while adults may only spend 20% of their sleep time in REM.
As you sleep the time you spend in REM sleep increases. For instance, the first time you go into REM sleep, it only typically lasts for 10 minutes. But you may spend up to one hour in REM sleep in the last sleep cycle of the night.