What is obstructive sleep apnoea (OSA; sleep apnoea)?

Obstructive sleep apnoea (OSA) is a condition characterised by episodes where a person’s breathing repeatedly stops while they sleep. ‘Apnoea’ refers to the lack of breathing, while ‘obstructive’ describes the cause of the apnoea.
During normal sleep, the muscles lining the upper throat relax slightly, but stay strong enough to keep the airway open, allowing air in and out of the lungs. Some individuals have a narrower passage, and during sleep, the relaxation of these muscles causes the passage to close, resulting in air not getting to the lungs. Loud snoring and laboured breathing occur.
When complete blockage of the airway occurs, air cannot reach the lungs. This tends to cause the sufferer to wake briefly (known as an ‘arousal’). This wakefulness restores the airway and the patient returns to sleep. This cycle can be repeated as many as 500 times each night, leaving the sufferer feeling tired and lethargic due to broken sleep.

Statistics on obstructive sleep apnoea

Obstructive sleep apnoea is thought to affect between 0.3-5% of people living in Western countries. The incidence of OSA is lower in women, with men affected 2-3 times more often. The incidence increases with age.

Risk factors for obstructive sleep apnoea

Major predisposing factors for OSA include:

  • Obesity: The incidence of sleep apnoea rises with increasing body mass index. This is probably because obese patients carry more fat in the soft tissues of the neck and throat, narrowing the airway;
  • Anatomical factors such as nasal obstruction, a large tongue and certain shapes of the palate and jaw can reduce the airway size and predispose to sleep apnoea;
  • Alcohol consumption worsens symptoms of obstructive sleep apnoea, but it is not known whether long-term alcohol consumption can lead to the development of OSA;
  • Cigarette smoking is also thought to increase the risk of obstructive sleep apnoea. This may be due to the chronic inflammatory effects of cigarette smoke on the lungs, or due to the nicotine-related changes in sleep quality.

Progression of obstructive sleep apnoea

If untreated, obstructive sleep apnoea may have serious consequences. Obstructive sleep apnoea affects the cardiovascular system due to the periods of poor oxygenation during sleep, and the stress on the body during attempts to re-initiate breathing. This may result in heart failure, arrhythmias (abnormal heart rhythms), or hypertension (high blood pressure).
Poor sleep due to recurrent arousals may result in excessive daytime sleepiness, personality changes, memory loss and intellectual impairment.

Symptoms of obstructive sleep apnoea

Night-time symptoms

  • Snoring, usually loud, habitual and bothersome to others, is found in almost all patients with obstructive sleep apnoea. However, not all snorers suffer from OSA;
  • Apnoeas (pauses in breathing) that often interrupt the snoring and end with a snort;
  • Gasping and choking sensations that intermittently arouse the patient from sleep;
  • Restless sleep, with patients often complaining of frequent arousal and tossing/turning during the night.

Daytime symptoms

  • Excessive tiredness, for example inability to stay awake while reading or watching television;
  • Waking without feeling refreshed;
  • Morning headache.

How is obstructive sleep apnoea diagnosed?

Pulse oximetry

Pulse oximetry is a technique which allows the oxygen saturation in the blood to be measured through a simple probe placed on the fingertip or ear. This can be performed overnight at home.
Patients with obstructive sleep apnoea will have cyclical drops in oxygen saturation during the night as they temporarily stop breathing. These can be recorded by the oximetry probe.
Diagnosis of OSA is made if more than 15 apnoeas (and corresponding drops in oxygen saturation) occur in any one hour of sleep.


In patients who have some, but not all, symptoms of obstructive sleep apnoea, or whose diagnosis is uncertain, pulse oximetry is not adequate to make a diagnosis of OSA. These patients require full investigation with polysomnography.
A polysomnogram is a sleep study. It should be conducted at a specialised sleep centre. Patients spend the night at the centre and various measurements are taken while they sleep. These measurements, which include assessment of brain activity (EEG), respiratory activity, airflow through the nose and mouth and pulse oximetry, give a better picture of any apnoeas which occur during sleep.

How is obstructive sleep apnoea treated?

Several simple lifestyle changes can reduce the symptoms of obstructive sleep apnoea in many patients. These changes include:

While some patients can be effectively managed with these lifestyle modifications, most patients with obstructive sleep apnoea will require further treatment. Options include:

  • Oral appliances: these are worn at night. They pull the jaw forward and are designed to prevent the collapse of the upper airway during sleep. They can be used for mild and moderate disease.
  • Continuous positive airway pressure (CPAP) via nasal mask: this is a machine which blows air through a mask into the patient’s mouth and nose during sleep. The pressure of the air keeps the throat open, preventing the airway from collapsing. It is the most effective treatment for obstructive sleep apnoea, reducing daytime sleepiness and improving sleep quality. However, some patients find the mask or feeling of pressure difficult to tolerate.
  • Surgical treatment is rarely used. Several procedures have been trialled, including uvulopalatopharyngoplasty (UPPP), which is designed to remove some of the soft tissues of the throat which collapse the airway during sleep. However, while UPPP may reduce snoring, it is often ineffective at treating true obstructive sleep apnoea.


More information

Sleep For more information about sleep, including how much is good for you, tips for getting more sleep, and sleep disorders, as well as some useful videos, see Sleep.


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