Sleep-stages

The quality of sleep in various sleep-stages.

We have five or six stages. (The jury is still out on the numbers) These stages are independent from one to another, each marked by subtle changes in bodily function and each part of a predictable cycle whose intervals are observable.

Stage 1 Drowsiness, the first in the stage when activities are reduced about 50%. Body activities slow down. The eyes are closed during this stage, but if aroused from it, a person may feel as if he or she has not slept. It may last for 5 to 10 minutes.

Stage 2 A period of light sleep during which positive and negative waves are present. Muscles are getting relaxed. The heart rate slows, and body temperature decreases. At this point, the body prepares to enter deep sleep.

Sleep-stages 3 and 4. The deep sleep-stage, Stage 4 being more intense than Stage 3. Slow delta waves are present. Non-REM Sleep. The period of non-Rapid Eye Movement sleep (NREM)is comprised of Stages 1-4 and lasts from 90 to 120 minutes. Surprisingly, Stages 2 and 3 repeat backwards before REM sleep is attained. So, a normal sleep cycle pattern: stage 1, 2, 3, 4, 3, 2, REM. Usually, REM sleep occurs 90 minutes after sleep onset.

Stage 5, REM This last stage is called REM or rapid eye movement. REM stage is also called as paradoxical sleep because it resembles an awaken state but the individual is not awake. Heart rate and respiration speed up and become erratic, while the face, fingers, and legs may twitch. Intense dreaming occurs during REM sleep and paralysis occurs simultaneously in the muscles of the chin and neck. The first period of REM typically lasts 10 minutes, with each recurring REM stage lengthening, and the final one lasting an hour.

Sleep Cycle. The five sleep-stages, including their repetition, is cyclical. A person may complete five cycles in a typical night's sleep.

Factors that Affect Sleep Stage and the Sleep Cycle

Sleep deprivation,

Frequently changing sleep schedule, such as night shift workers.

Stress,

Environment,

These all affect the progression of the sleep-stages. Rapid eye movement latency (the time it takes a person to achieve REM sleep) may be affected by a sleep disorder like narcolepsy.

Depression shortens the duration of rapid eye movement.

Antidepressants like ProzacŪ may quicken sleep onsets and lengthen REM stages. In some cases, people who take antidepressants benefit from the effects they have on the quality and duration of the sleep cycle.

Age.

The percentage of REM sleep is highest during infancy and early childhood, drops off during adolescence and young adulthood, and decreases in older age. Sleep change relative to age. Stages 3 and 4 in the first sleep cycle shorten in older people. Older people get less total deep sleep than younger people do. Also with age comes the lengthening of the first REM stage. Older people commonly enter REM sleep quicker and stay there longer.

back to Home Page