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Sleep Apnoea

Sleep Apnoea1. What is sleep apnoea?
2. What happens during OSA?
3. Symptoms of sleep apnoea
4. Causes of sleep apnoea
5. Known risk factors for OSA

What is sleep apnoea?

Obstructive sleep apnoea (OSA) is a condition which causes interruptions in breathing during sleep.

For people with OSA, two types of interruptions to breathing can occur. These are described below.

Apnoea: during an apnoea, the muscles in the throat relax and cause a total blockage of the throat's airway. An apnoea usually lasts for around 10 seconds.

Hypopnoea: a hypopnoea is a partial blockage of the airway, which halves the amount of oxygen that is taken into the body. As with an apnoea, hypopnoea also usually last for around 10 seconds. (Because of these episodes of hypopnoea, doctors sometimes use the term 'obstructive sleep apnoea hypopnoea syndrome').The term 'obstructive' is used to distinguish OSA from rarer forms of sleep apnoea, such as central sleep apnoea, which is caused by the brain 'forgetting' to breathe during sleep.

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What happens during OSA?

People with OSA may experience repeated episodes of both apnoea and hypopnoea during the night. The lack of oxygen causes a person to come out of deep sleep into a lighter stage of sleep, or a brief period of wakefulness, in order to restore their normal breathing. However, once they fall back into deep sleep further episodes of apnoea and hypopnoea can occur.

The repeated interruptions to sleep that are caused by OSA can lead to the person feeling very tired during the day. A person with OSA will usually have no memory of any episodes of breathlessness, so they are often unaware that they are not getting a proper night's sleep.

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Symptoms of sleep apnoea

Most people with obstructive sleep apnoea (OSA) will snore loudly. Their partners may notice that their breathing is laboured and noisy and it can often be interrupted by gasping and snorting as they experience an episode of apnoea.

If you have OSA you may have no memory of your sleep being interrupted but you will wake feeling that you have not had a decent night's sleep.

Over time, the repeated interruptions to your sleep will lead to the symptoms of sleep deprivation. These include:

  • feeling excessively sleepy during the day,
  • poor memory and concentration,
  • headaches; particularly in the morning,
  • irritability and short temper,
  • depression,
  • lack of interest in sex, and
  • in men, impotence (inability to get or maintain an erection).

Some people with OSA may also find that they wake up frequently during the night in order to urinate.

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Causes of sleep apnoea

Obstructive sleep apnoea (OSA) is caused by the muscles in the back of your throat relaxing during sleep. These muscles support your tongue, tonsils and soft palate (a muscle at the back of the throat used in speech).

Once the muscles relax, the airway in your throat can narrow or become totally blocked. This interrupts the oxygen supply to your body which triggers your brain to pull you out of deep sleep so that your airway can be reopened and you can breathe normally.

As you need to have a certain amount of deep sleep in order for both your body and your mind to be fully refreshed, only having limited episodes of deep sleep will lead to you feeling very tired the next day.

Most adults require at least eight hours of sleep to function at their best and 50% of that time should be spent in the deepest phase of sleep.

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Known risk factors for OSA

The known risk factors for OSA are outlined below.

  • Obesity - the more obese you are, the higher the risk. For example, a 10% increase in your weight will lead to a six-fold increase in your risk of developing OSA.
  • Being male - the reasons why OSA is more common in men than in women are unknown.
  • Being 40 years of age or over.
  • Having a large neck - people with OSA often have a neck circumference of 43 cm (17 inches) or more,
  • Taking medicines that have a sedative effect - such a sleeping pills, or tranquillisers,
  • Having an unusual inner-neck structure - such as an unusually narrow airway or unusually large tonsils or tongue or having a lower jaw that is set back further than normal.

Suspected risk factors for OSA

Experts have also identified a number of suspected risk factors that they believe may also contribute to OSA. These are described below.

  • Drinking alcohol before bedtime.
  • Smoking.
  • Being menopausal - the changes in hormone levels that occur during the menopause may cause the throat muscles to relax.
  • Having a family history of OSA - there may be some genes that you inherit from your parents that can make you more susceptible to OSA.
  • Taking the anti-impotence medicine sildenafil (Viagra) - there is some evidence to suggest that sildenafil can cause the throat muscles to relax.

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