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Obstructive sleep apnoea

Page last reviewed: 13/07/2011

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 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. We do not have detailed data on the number affected in Ireland.

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.


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.

Stages of sleep

Sleep can be divided into two categories:

  • rapid eye movement (REM) sleep usually occurs around 90 minutes after falling asleep; during REM sleep, brain activity increases and dreaming occurs; a number of periods of REM can occur during a night’s sleep (usually three to five episodes)
  • non-rapid eye movement (NREM) sleep is made up of four different stages (see below); one sleep cycle may consist of several stages of NREM sleep followed by a period of REM sleep.

There are four different stages of NREM sleep.

  • Stage 1 (drowsiness) may last 5 to 10 minutes, during which time your muscles relax and you may be easily disturbed. You may also feel as if you are falling, which causes a muscle contraction known as hypnic myoclonia or ‘sleep jerks’.
  • Stage 2 (light sleep): eye movements stop during this stage, your heart rate slows down and your body temperature decreases as your body prepares itself for deep sleep.
  • Stages 3 and 4 (deep sleep): these two stages are deep sleep. Stage 4 is more intense than stage 3. During these stages, your physical energy levels are restored and your immune system is strengthened. If woken, you may feel disorientated for a few minutes. Around 90 minutes into this sleep cycle you will begin to have REM sleep.

Page last reviewed: 13/07/2011

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

If you have OSA, you may have no memory of your interrupted breathing during the night. However, when you wake up you are likely to feel as though you have not had a good night's sleep.

Symptoms of OSA include:

  • feeling very sleepy during the day
  • waking up with a sore or dry throat
  • poor memory and concentration
  • headaches (particularly in the morning)
  • irritability and a short temper
  • anxiety
  • depression
  • lack of interest in sex
  • in men, impotence (inability to get or maintain an erection)

Some people with OSA may also wake up frequently during the night to urinate.


As someone with OSA can suffer a lack of refreshing sleep, they run an increased risk of being involved in a life-threatening accident, such as a car crash. Their risk of having a work-related accident also increases.

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

If you have OSA, it could affect your ability to drive. It is important that you inform your doctor and the Road Safety Authority (RSA) about a condition which could impact on your driving ability.

Page last reviewed: 13/07/2011

Obstructive sleep apnoea (OSA) is caused by the muscles and soft tissue in the back of your throat collapsing inwards during sleep. These muscles support your tongue, tonsils and soft palate (a muscle at the back of the throat that is 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 reopens and you can breathe normally.

Risk factors

There are a number of risk factors for OSA, described below.

  • Being overweight is a major risk factor because excessive body fat increases the bulk of soft tissue in the neck, which can place a strain on the throat muscles; excess stomach fat can also lead to breathing difficulties, which can make OSA worse.
  • Being male - it is not known why OSA is more common in men than in women, but it may be related to different patterns of body fat distribution.
  • Being 40 years of age or more - although OSA can occur at any age, it is more common in people who are over 40 years old.
  • Having a large neck - a man of average height (1.7m or 5ft 8in) with a collar size that is greater than 45cm (18 inches) is classed as obese and has an increased risk of developing OSA.
  • Taking medicines that have a sedative effect, such a sleeping tablets or tranquillisers.
  • Having an unusual inner-neck structure, such as an unusually narrow airway, unusually large tonsils or tongue, or having a small lower jaw that pushes the tongue backwards.
  • Having excess folds in the inner lining of the mouth (mucous membrane).
  • Alcohol - drinking alcohol can make snoring and sleep apnoea worse.
  • Smoking - you are three times more likely to develop sleep apnoea if you smoke.
  • Being menopausal - the changes in hormone levels during the menopause may cause the throat muscles to relax.
  • Having a family history of OSA - there may be genes inherited from your parents that can make you more susceptible to OSA.
  • Diabetes - OSA is three times more common in people with diabetes.
  • Nasal congestion - OSA occurs twice as often in people with nasal congestion, which may be due to the airways being narrowed.

Page last reviewed: 13/07/2011

If you have symptoms of excessive daytime sleepiness, such as feeling drowsy, a lack of energy and poor memory, ask a partner, friend or relative to observe you while you are asleep. They may be able to spot episodes of breathlessness that could help to confirm a diagnosis of obstructive sleep apnoea (OSA).

Physical examination and tests

Visit your GP. They will ask you a number of questions about your symptoms, such as whether you regularly fall asleep during the day against your will.

Your GP will also carry out a physical examination and some tests, including a blood pressure test. A blood test is also likely to be arranged.

A physical examination and tests are carried out to rule out other conditions that could explain your tiredness, such as hypothyroidism (an underactive thyroid gland).

The next step is to observe you while you are asleep. To do this, you may be asked to spend a night at a sleep centre so that any events that indicate OSA can be monitored. This is known as polysomnography (see below).

Alternatively, you may be given a monitoring device to wear at night while you sleep at home (a home sleep study). The device is returned to the sleep centre the following day so that the recorded information can be downloaded by staff.

Testing at a sleep centre

Sleep centres are specialist clinics or hospital departments that help treat people with sleep disorders.


The main investigation into your sleep is polysomnography. This investigation will enable sleep specialists to decide what is the best treatment for you.

During polysomnography, specialist nurses will place a series of electrodes on the surface of your skin (this is painless) and bands on other areas. Electrodes and bands are placed on the following areas:

  • electrodes on your face and scalp
  • electrodes above your lip
  • bands around your chest
  • bands around your abdomen (tummy)

Sensors will also be placed on your legs, and an oxygen sensor will be attached to your finger.
The tests that are carried out during a polysomnography include:

  • electro-encephalography (EEG) - this monitors your brain waves
  • electromyography (EMG) - this monitors your muscle tone
  • recording thoracoabdominal movements (movements in your chest and abdomen)
  • recording oronasal airflow (the airflow in your mouth and nose)
  • pulse oximetry - this measures your heart rate and blood oxygen levels
  • electrocardiography (ECG) - this monitors your heart
  • sound and video recording to record your breathing and snoring, and your behaviour during the night

Polysomnography must be done by experienced technicians in a hospital or sleep centre.

During the testing process, specialist sleep nurses will monitor the signals. If OSA is diagnosed during the early part of the night, you may be given continuous positive airway pressure (CPAP) treatment. CPAP involves using a mask that delivers constant compressed air to the airway and stops the airway from closing, which prevents OSA.

See Sleep apnoea - treatment for more information about CPAP treatment.
Once the tests have been completed, staff at the sleep centre should have a good idea about whether or not you have OSA. If you do, they can determine how much it is interrupting your sleep and recommend appropriate treatment.

Apnoea-hypopnoea index (AHI)

The severity of OSA is determined by how many episodes of apnoea and hypopnoea you experience over the course of an hour. These episodes are measured using the apnoea-hypopnoea index (AHI).

The severity of OSA is measured using the following criteria:

  • mild - an AHI reading of 5 to 14 episodes an hour
  • moderate - an AHI reading of 15 to 30 episodes an hour
  • severe - an AHI reading of more than 30 episodes an hour

An AHI reading of less than 10 is unlikely to be linked to a clinical problem or sleep disorder.

Home study

A home sleep study is a possible option. However, you will still need to visit a specialist sleep centre during the day to learn how to use the home study equipment.
You will need to learn how to use portable recording equipment, which includes:

  • a breathing sensor
  • sensors to monitor your heart rate
  • oxygen sensors that are put around your finger and bands around your chest

The equipment records levels of oxygen, breathing movements, heart rate and snoring.

After you have used this equipment overnight, you will need to take it to the sleep centre, where the information will be downloaded onto a computer and analysed by sleep specialists.

If more information about sleep quality is required by the sleep centre, a polysomnography will be required, which will be carried out at the sleep centre.

Page last reviewed: 13/07/2011

Lifestyle changes

Mild cases of obstructive sleep apnoea (OSA) can often be treated by making lifestyle changes, such as:

  • losing weight (if you are overweight or obese)
  • stopping smoking (if you smoke)
  • limiting your alcohol consumption

 The recommended limits for alcohol consumption are 17 standard drinks a week for men and 11 for women. A standard drink of alcohol is equal to about half a pint of beer, a small glass of wine or a pub measure of spirits

See the Health A-Z topic about Quitting smoking for more information, support and advice about giving up smoking.
Sleeping on your side, rather than on your back, may also help to relieve the symptoms of OSA, although it will not prevent the condition.

See Sleep apnoea - prevention for more information about lifestyle changes that can help prevent sleep apnoea.

Continuous positive airway pressure (CPAP)

Moderate to severe cases of sleep apnoea may need to be treated using a type of treatment called continuous positive airway pressure (CPAP). This involves using breathing apparatus to assist with your breathing while you are asleep.

CPAP is used at night when you are asleep. A mask is placed over your nose, which delivers a continuous supply of compressed air. The compressed air prevents the airway in your throat from closing.

Earlier versions of CPAP often caused nasal dryness, nose bleeds and a sore throat. However, the latest version includes a humidifier (a device that increases moisture) which helps to reduce these side effects.

If CPAP causes you discomfort, inform your treatment staff because the device can be modified to make it more comfortable. For example, you can try using a CPAP machine that starts with a low air pressure and gradually builds up to a higher air pressure as you fall asleep.
As CPAP can feel peculiar to start with, you may be tempted to abandon the treatment. However, people who persevere with it quickly get used to wearing the mask, and their symptoms improve significantly. It reduces blood pressure and the risk of stroke by 40%, and lowers the risk of cardiac (heart) complications by 20%.
Possible side effects of CPAP include:

  • mask discomfort
  • nasal congestion, runny nose or irritation
  • difficulty breathing through your nose
  • headaches and ear pain
  • stomach pain and flatulence (wind)

If you have any of these side effects, discuss them with your sleep specialist who may be able to recommend an alternative treatment.

Mandibular responding splint (MRS)

A mandibular responding splint (MRS) is sometimes referred to as a mandibular advancement device or MAD. It is a dental appliance, similar to a gum shield, and is used to treat mild sleep apnoea.
A MRS is worn over your teeth when you are asleep. It is designed to hold your jaw and tongue forward to increase the space at the back of your throat and reduce the narrowing of your airway that causes snoring.
A MRS can be made for you by an orthodontist (a dental specialist) using impressions of your teeth and jaw.

If you have a MRS, avoid using hot water to clean it because this will damage it. Use cold water and a soft brush. A MRS may not be suitable treatment for you if you do not have many (or any) teeth. If you have dental caps, crowns or bridgework, consult your dentist to ensure that they will not be unduly stressed or damaged by a MRS.


Surgery to treat OSA is usually not recommended because evidence shows that it is not as effective as CPAP in controlling the symptoms.

Therefore, surgery for OSA is usually considered as a last resort when all other treatment options have failed and if OSA is severely affecting your quality of life.

Surgical removal of enlarged tonsils could be a helpful as a primary treatment in selected cases, particularly children.

Correction of a deviated nasal septum has limited efficacy as a primary treatment of OSA but may be helpful in facilitating CPAP therapy in selected patients where CPAP is compromised by nasal obstruction.

Soft-palate implants

Soft-palate implants make the soft palate (part of the roof of the mouth) stiffer and less likely to vibrate and cause an obstruction. The implants are thin and are inserted into the soft palate under local anaesthetic (the area of your body being operated on is numbed so that you do not feel any pain). You will, however, remain awake during the procedure). These implants are particularly indicated for snoring and there is little evidence of benefit in OSA.
The National Institute of Health and Clinical Excellence (NICE) have said that soft-palate implants are safe, but they are not recommended for treating OSA because there is a lack of evidence about their effectiveness. However, in exceptional cases, this form of treatment is recommended for treating snoring that is associated with sleep apnoea.

Page last reviewed: 13/07/2011

High blood pressure

Many people with obstructive sleep apnoea (OSA) develop high blood pressure (hypertension). If you have high blood pressure, your risk of developing cardiovascular diseases, such as a heart attack or stroke, is also increased.

While there is increasing evidence that OSA represents a significant independent risk factor for hypertension, other co-existing risk factors such as obesity are also important.

Maintaining a healthy weight, taking regular exercise and eating a healthy, balanced diet is the best way of preventing hypertension.

See the Health A-Z topic about High blood pressure for more information about this condition.

Other medical conditions

If OSA is left untreated, hypertension also increases your risk of developing other serious conditions, including:

  • heart attack - a serious condition that is caused by a blood clot blocking the supply of blood to the heart
  • stroke - a serious medical condition that is caused by a disturbance in the blood supply to the brain
  • obesity - a condition in which a person is carrying too much body fat for their height and sex
  • type 2 diabetes - a long-term condition that is caused by too much sugar (glucose) in the blood.

Page last reviewed: 13/07/2011

Lifestyle changes

Some cases of mild to moderate OSA can be successfully prevented by making changes to your lifestyle. These include:

  • losing weight if you are overweight or obese
  • avoiding alcohol during the evening
  • quitting smoking if you smoke (see below)
  • avoiding the use of sleeping tablets and tranquillisers
  • not sleeping on your back because this can make snoring worse

See the Health A-Z topic about Quitting smoking for more information and advice about giving up smoking, plus details of the support that is available to help you quit.

Improving overall sleep quality

Other changes you can make to improve the quality of your sleep include:

  • reducing the amount of light and noise in your bedroom
  • not reading or watching television in bed
  • keeping work-related activities outside of the bedroom
  • relaxing before going to bed

See the Health A-Z topic about Insomnia for more information and advice about the condition.


Content provided by NHS Choices www.nhs.uk and adapted for Ireland by the Health A-Z.

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