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Types of sleep disorders

Sleep disorders describe problems people have getting to sleep, staying asleep, getting enough sleep and disturbances during sleep. Getting enough sleep is important for our overall health, so seek medical advice if you have a sleep problem.

Sleep can be divided into two types: rapid eye movement (REM) sleep and non-REM (NREM) sleep. NREM sleep has four stages of increasingly deep sleep. Stage 1 sleep is the lightest, while stage 4 is the deepest.

During normal sleep, you move cyclically through these types and stages of sleep. But if your sleep is repeatedly interrupted and you are unable to progress normally through REM and NREM sleep, you may feel tired, fatigued, and have trouble concentrating and paying attention while awake. Sleepy individuals are more likely to have accidents while driving, as well as other types of accidents.

If you have trouble getting to sleep or sleeping through the night, if you wake up too early or find it hard to wake up at all, or if you are exceptionally tired during the day, you may have one of the following sleep problems.

Circadian rhythm disorders

It is normal for people to sleep at night - thanks not only to the conventions of the 'nine-to-five' working day, but also to the close interaction between our natural sleep and alertness rhythms, which are driven by an internal 'clock'.

This clock is a small part of the brain called the suprachiasmatic nucleus of the hypothalamus. It sits just above the nerves leaving the back of our eyes. Light and exercise "reset" the clock and can move it forward or backward. Abnormalities related to this clock are called circadian rhythm disorders ("circa" means "about," and "dies" means "day").

Circadian rhythm disorders include jet lag, adjustments to shift work, delayed sleep phase syndrome (you fall asleep and wake up too late), and advanced sleep phase syndrome (you fall asleep and wake up too early).


People who have insomnia don't feel as if they get enough sleep at night. They may have trouble getting to sleep or may wake up frequently during the night or early in the morning. Insomnia is a problem if it affects your daytime activities. Insomnia has many possible causes, including stress, anxiety, depression, poor sleep habits, circadian rhythm disorders (such as jet lag), and taking certain medicines.

Insomnia may be temporary and stem from a simple cause, such as jet lag. Short-term insomnia may also be caused by an illness, a stressful event, or drinking too much coffee. Many medications have insomnia as a side effect.

Long-term insomnia may be caused by stress, depression, and anxiety. People can also become conditioned to insomnia - they associate bedtime with difficulty, expect to have trouble sleeping (and thus do), and become irritable (which can cause more insomnia).

This cycle can be maintained for several years.

Circadian rhythm disorders are an important but less common cause of insomnia.

People who abuse alcohol or drugs often suffer from insomnia.

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