Obstructive sleep apnoea (OSA) is a condition that causes interrupted breathing during sleep.

There are two types of breathing interruption characteristic of OSA:

• 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 airflow reduction of greater than 50% for 10 seconds or more

Sleep apnoea is associated with being overweight, and other risk factors. Read more about the causes of sleep apnoea.

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.

What happens during OSA?

During the night, people with OSA may experience repeated episodes of apnoea and hypopnoea.

During an episode, 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.

Most people with OSA snore loudly. Their breathing may be noisy and laboured and it is often interrupted by gasping and snorting with each episode of apnoea.

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.

Read more about the symptoms of sleep apnoea.

How common is OSA?

OSA is a relatively common condition that affects more men than women. In the UK, it is estimated that around 4% of middle-aged men and 2% of 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. It is estimated that up to 5% of adults have undiagnosed OSA.

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.

Lifestyle changes, such as losing excess weight, can often help mild cases of sleep apnoea to resolve. In more severe cases, the use of breathing apparatus while sleeping may be necessary.

Read more about how sleep apnoea is treated.

Left untreated, OSA can increase the risk of:

• high blood pressure (hypertension)
• heart attack
• stroke
• obesity
• type 2 diabetes

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.

Read more about the complications of sleep apnoea.