Sleep Stages and Lifespan Changes in Sleep

Sleep Stages

Each sleep cycle is approximately 90 minutes in length and most people experience 5-6 cycles per night. Stages 1 to 4 are slow wave sleep (SWS) and stage 5 is rapid eye movement sleep (REM).

·         STAGE ONE

o    Muscles are very active and we are still alert.

o    When entering a hypnogogic state, people often experience a jumping sensation.

o    In this stage, you are easily woken.

o    Lasts for approximately 15 minutes.

·         STAGE TWO

o    Muscles become less active and you are more relaxed.

o    Brief bursts of activity.

o    Harder to be woken, but still possible.

o    Lasts for approximately 20 minutes.

·         STAGE THREE

o    Slight activity and difficult to wake.

o    Lasts for about 15 minutes.

·         STAGE FOUR

o    Eye movement starts to speed up.

o    Difficult to wake.

o    Lasts for around 30 minutes.

·         REM

o    Muscles twitch but barely active.

o    Brain activity increases and rapid eye movement begins.

o    Bodily processes, such as heart rate and temperature, drop but pick up near the end of the stage.

o    Brain waves are desynchronised and you enter a paradoxical state, where your muscles are paralysed.

Lifespan Changes

·         Infancy

o    Babies sleep for about 16 hours a day but not continuously, they wake up every hour or so and their cycle is shorter than an adults.

o    They experience two types of sleep:

§  Active (REM) sleep

§  Quiet (SWS) sleep

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