• Sleep is regulated by an internal body ‘clock’ inside the brain.
  • There are various distinct stages of sleep, repeated throughout the night at 90 to 120 minute cycles.
  • Severe sleep disorders should be investigated and treated at a sleep disorder centre.
Sleep is a state of consciousness that happens every 24 hours. It is a period of rest and recuperation for the body and much needed ‘down time’ for the brain.

People vary in the amount of sleep they need, depending on their age, lifestyle, diet, personality and environment. Generally, we sleep less as we age and our sleep tends to be more broken. Newborn babies tend to sleep for around 16 hours out of every 24, while adults average eight hours and the elderly sleep a little less.

The body clock

Sleep is regulated by an internal ‘clock’, which is tuned by the day-night cycles (circadian rhythm). When the sun sets, your brain starts to release ‘sleepy’ chemicals, until eventually you feel the need to retire for the night. In the morning, exposure to daylight prompts your brain to reduce ‘sleepy’ and release ‘awake’ chemicals.

Sleep stages

Sleep isn’t a static state of consciousness. We all go through various distinct stages of sleep, over and over, every night. Generally, the brain moves from light sleep to deeper sleep and eventually to rapid eye movement, or REM, sleep. REM sleep occurs regularly, about once every 90 to 120 minutes.

Brain waves in REM sleep are faster than in non-REM sleep. REM sleep is associated with dreaming and with stimulation of the parts of the brain used for learning, while body repair and growth tends to happen during non-REM sleep. It is important to get the right mix of both REM and non-REM sleep to maintain your natural sleep cycle and help you wake rested and refreshed.

Common sleep disorders

Sleep is a complicated state of consciousness, since it can be disturbed in so many ways. Some of the more common sleep complaints include:
  • Insomnia – refers to difficulties in getting to sleep or staying asleep. It is the most common sleep disorder in adults.
  • Jet lag – a different time zone throws off the body’s internal clock, which takes a few days to reset. Working night shift can mimic the symptoms of jet lag.
  • Narcolepsy – is extreme tiredness with intermittent sleepiness during the day, which can include involuntary napping.
  • Periodic limb movement disorder – is muscle spasms of the legs that may wake up the sleeper. This is more common in the middle-aged and elderly.
  • Restless legs – is discomfort in the lower legs, which gets better with movement and gets worse later in the day makes the person need to move their legs or get up and walk around.
  • Snoring – is noisy breathing caused by a narrow throat and nose. It is more common in males.
  • Sleep apnoea – the upper airway is blocked, causing airflow and breathing to stop for a time during sleep.
  • Sleep starts – is the common feeling of muscle jerks or a sensation of falling that happens when a person is just going off to sleep.
  • Sleepwalking – tends to affect children more than adults.
  • REM sleep behaviour disorder – the sleeper tends to act out what’s happening in their dreams, which could mean punching or kicking.

Treatment for sleep disorders

Some disorders such as sleepwalking, sleep starts and snoring often don’t require any treatment because they are harmless. Lifestyle changes can help relieve mild or occasional symptoms if they are causing an unwanted disruption to your life.

Insomnia, the most common form of sleep complaint, is a symptom, not a diagnosis, and, requires assessing and treatment of the cause (or causes) rather than the insomnia itself. Some of the more involved sleep disorders need to be treated at a sleep disorder clinic. While snoring alone may be harmless (benign snoring), it may indicate the presence of a more serious medical condition – obstructive sleep apnoea.

Where to get help

  • Your doctor
  • Sleep disorder clinic

Things to remember

  • Sleep is regulated by an internal body ‘clock’ inside the brain.
  • There are various distinct stages of sleep, repeated throughout the night at 90 to 120 minute cycles.
  • Severe sleep disorders should be investigated and treated at a sleep disorder centre.

More information


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Last updated: June 2014

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