Obstructive sleep apnoea (OSA) is a condition that causes interrupted breathing during sleep. For people with OSA, two types of breathing interruptions have been defined:
- apnoea - the muscles and soft tissues in the throat relax and collapse sufficiently to cause a total blockage of the airway; it is called an apnoea when the airflow is blocked for 10 seconds or more
- hypopnoea - a partial blockage of the airway that results in an air flow reduction of greater than 50% for 10 seconds or more
Because of the episodes of hypopnoea that occur during OSA, doctors sometimes refer to the condition as 'obstructive sleep apnoea-hypopnoea syndrome'. The term 'obstructive' distinguishes OSA from rarer forms of sleep apnoea, such as central sleep apnoea, which is caused by the brain 'forgetting' to breathe during sleep.
Sleep
Sleep is driven by natural brain activity. You need to have a certain amount of deep sleep for your body and mind to be fully refreshed. Having only limited episodes of deep sleep will leave you feeling very tired the next day.
In order to function properly, most adults need seven to eight hours of sleep. Around 15-25% of that time should be spent in the deepest phase of sleep, known as slow wave sleep (see box).
What happens during OSA?
During the night, people with OSA may experience repeated episodes of apnoea and hypopnoea.
The lack of oxygen causes the person to come out of deep sleep and into a lighter state of sleep, or a brief period of wakefulness, in order to restore normal breathing. However, after falling back into deep sleep, further episodes of apnoea and hypopnoea can occur. Such events may occur more than once a minute throughout the night.
The repeated interruptions to sleep caused by OSA can make the person feel very tired during the day. A person with OSA will usually have no memory 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 around 4 in 100 middle-aged men and 2 in 100 middle-aged women have OSA.
The onset of OSA is most common in people aged 35 to 54 years old, although it can affect people of all ages, including children. The condition often goes undiagnosed. Only one in four people with obstructive sleep apnoea are diagnosed with the condition.
Studies have also shown that 60% of people over 65 years old have OSA.
Outlook
OSA is a treatable condition and there are a variety of treatment options to reduce the symptoms. Left untreated, OSA can increase the risk of:
- high blood pressure (hypertension)
- heart attack
- stroke
- obesity
- type 2 diabetes
See Sleep apnoea - complications for more information about these conditions.
Untreated OSA also increases a person’s risk of developing heart failure and irregular heartbeats, and it can lead to poor performance at work and at school.
