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.

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.

How common is OSA?

OSA is a relatively common condition that affects men more than women. In the UK, it is estimated that about 3.5% of men and 1.5% of women have OSA. The condition is most common in people aged 40 or over, although it can affect people of all ages, including children.

Obesity is a major risk factor for OSA because excessive body fat can place strain on the muscles in the throat.

OSA is a serious condition

As someone with OSA can experience a lack of proper sleep, their risk of being involved in a life-threatening accident, such as a car crash, is increased.

There is also some evidence to show that those with OSA are at greater risk of developing high blood pressure (hypertension), which can lead to a heart attack or stroke.

Research has shown that someone who has been deprived of sleep due to OSA has the same impairment in judgement and reaction time as someone who is over the drink-drive limit.