Normal Sleep Patterns and the Stages of Sleep

The human body runs on an internal clock. The entire cycle--transitioning from wakefulness to sleep and back to wakefulness--is known as the circadian rhythm and lasts approximately 24 hours. During this cycle, people experience daily hormonal and body temperature fluctuations. The circadian rhythm helps most people achieve normal sleep patterns.
Individuals who experience normal sleep patterns generally feel energetic during the day. Disrupted sleep cycle stages cause people to operate slower than normal, reducing work or academic productivity.
Normal sleeping patterns also encourage healthy immune responses, helping the body stave off disease and infection. Adequate sleep is also essential for children's mental and physical growth.
People who experience sleep disorders may not have normal sleep patterns. Normal sleeping patterns can be disrupted by many factors, including mental and physical health, lifestyle and age. Treatment for sleep disorders may focus on ways to encourage healthy, restful sleep.

Basics of Normal Sleeping Patterns

Two types of sleep emerge during an average night: rapid eye movement (REM) sleep and non-REM sleep (NREM). Non-REM sleep includes four sleep cycle stages in which individuals slide from drowsiness into a deep sleep before passing into REM sleep and dreaming.
The brain experiences periods of intense activity during REM sleep, when dreaming takes place, while the body's muscles remain in a paralyzed state to prevent physical movement in the dream stage.

Stages of Sleep

During a typical night, the average person experiences several stages of sleep:
  • The waking stage precedes NREM sleep cycle stages.
  • Stage 1: The individual is drowsy and easily awakened. Muscles begin to relax and eye activity is slow. This stage lasts about 5 minutes.
  • Stage 2: Also known as the "light sleep" stage, stage 2 lasts about 25 minutes. During this stage, eye movement stops, internal temperature drops and heart rate decreases.
  • Stages 3 and 4: Deep sleep cycles, known as "delta" or "slow-wave," stages of sleep are progressively intense. In these stages, a person is difficult to wake.
  • REM sleep: REM sleep involves rapid eye movement and dreaming. Brain activity resembles the waking state. A person may experience several episodes of REM sleep every night.
In general, people experience deeper, more restful sleep earlier in the night, and lighter sleep during the second half of the night. As people age, they tend to spend more time in REM sleep. Factors such as depression, stress or prescription medications can also lead to disruptions in normal sleeping patterns.
Problems with normal sleep patterns can result in a variety of sleep disorders, such as nightmares, sleepwalking, night terrors, narcolepsy and REM sleep behavior disorder. People who do not have normal sleeping patterns or experience less than ideal sleep should talk to a doctor, who can recommend appropriate treatments--such as prescription medication or improved sleep hygiene--that may help improve sleep patterns. Keeping a sleep diary may also help identify problems with normal sleeping patterns.

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