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Sleep Apnoea - What is it?

Sleep apnoea is a condition where you may have breathing pauses when you are asleep. The word apnoea means without breath - that is, the breathing stops. In sleep apnoea, your breathing stops because of an obstruction to the flow of air down your airway and into your lungs. You may also have episodes where your breathing becomes slower and shallower. This is called a hypopnoea. Because there can also be combined episodes of apnoeas and hypopnoeas, healthcare professionals sometimes use the term 'obstructive sleep apnoea/hypopnoea syndrome.

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What causes sleep apnoea?

When you sleep, the throat muscles relax and if you have sleep apnoea, your throat muscles become so relaxed during sleep that a narrowing or even a complete closure of your airway may occur.

When your airway is narrowed and the airflow is reduced, at first this can cause snoring. If there is a complete closure then your breathing actually stops (apnoea) for around 10 seconds or more your blood oxygen level then may drop and your brain detects this. Your brain then tells you to wake up and make an extra effort to breathe. Then your breathing starts again with some deep breaths. You will normally go back off to sleep again quickly and will not be aware that you have woken up.

Sometimes, the airway can just partially collapse and can lead to a hypopnoea. Breathing becomes abnormally slow and shallow. If this happens, the amount of oxygen that is taken into your body can be halved. Hypopnoea episodes also usually last for around 10 seconds or more.

If someone watches you sleeping they may notice that you stop breathing for a short time and then make a loud snore or a snort. You might even sound as if you are suddenly choking, briefly wake up and then get straight back off to sleep.

It is quite common to have the odd episode of apnoea when asleep, often finishing with a snort. This is of no concern. In fact, some people when they sleep have periods of 10-20 seconds when they do not breathe. However, people with sleep apnoea have many such episodes during the night. For a  diagnosis of sleep apnoea, you need to have at least five episodes of apnoea, hypopnoea, or both events per hour of sleep. However, there are different levels of severity of sleep apnoea (mild, moderate or severe).

Obstructive sleep apnoea syndrome is usually classified as:

  • Mild sleep apnoea - between 5-14 episodes an hour.

  • Moderate sleep apnoea - between 15-30 episodes an hour.

  • Severe sleep apnoea - more than 30 episodes an hour.

So, if you have sleep apnoea, you may wake up many times during the night. You will not remember most of these episodes but your sleep will have been greatly disturbed. As a consequence, you will usually feel sleepy during the day. Daytime sleepiness in someone who is a loud snorer at night is the classic hallmark of someone who may have sleep apnoea.

Who can get Sleep Apnoea?

Sleep apnoea syndrome can occur at any age, including in children. It most commonly develops in middle-aged men who are overweight or obese, although it can affect people who are not overweight. It is thought that as many as 4 in 100 middle-aged men and 2 in 100 middle-aged women develop sleep apnoea.

Factors that increase the risk of developing sleep apnoea or can make it worse include the following. They all increase the tendency of the narrowing in the throat at night to be worse than normal.


  • Being overweight or obese, particularly if you have a thick neck, as the extra fat in the neck can squash your airway.

  • Drinking alcohol in the evening. Alcohol relaxes muscles more than usual and makes the brain less responsive to an episode of apnoea. This may lead to more severe apnoea episodes in people who may otherwise have mild sleep apnoea.

  • Enlarged tonsils.

  • Taking sedative medicines such as sleeping tablets or tranquilisers.

  • Sleeping on your back rather than on your side.

  • Having a small or receding lower jaw (a jaw that is set back further than normal).

  • Smoking.

  • You may also have a family history of sleep apnoea

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