Sleep disordered breathing
The term ‘sleep disordered breathing’ refers to a range of conditions that result in abnormal breathing during sleep. The most common is sleep apnoea. Apnoea means a temporary pause in breathing. Although there are other types of apnoea, the term ‘sleep apnoea’ usually refers to obstructive sleep apnoea syndrome (OSAS) in which the individual is briefly unable to breathe due to temporary obstruction of the airway in the throat, called the pharynx. In patients with OSAS this may occur many hundreds of times during a single night’s sleep.
When we are asleep, our muscles are relaxed. In some people, the tongue and the relaxed muscles in the throat can cause a narrowing of the airway, which restricts breathing and can stop it temporarily. If this happens, the brain causes brief partial awakening, which reopens the airway and restarts breathing. Repeated awakenings in the night can seriously affect the quality of sleep, leading to excessive daytime sleepiness.
In addition, each apnoea is accompanied by a surge in heart rate and blood pressure. Eventually the increased blood pressure (hypertension) persists even when awake and this increases the risk of a heart attack or a stroke.
Snoring is universal in people with OSAS. The noise of snoring arises from vibration of the tissues in the throat, implying that the airway is potentially unstable and therefore more vulnerable to collapse during sleep. However, only a minority of snorers have OSAS.
Symptoms of OSAS can occur both day and night:
- Excessive sleepiness
- Lack of concentration
- Morning headache
- Changes in mood
- Dry mouth
- Impotence or a decreased sex drive
- Restless sleep
- Awaking with choking
- Vivid dreams
- Nocturia (urination at night)
- Salivating and teeth grinding
The prevalence of sleep apnoea increases with age up to 60 years.
Anything causing the throat to be narrower than average can increase the likelihood of OSAS:
Moderate or severe obesity is a major risk factor as it is accompanied by an increase in the fatty tissue around the throat. Obesity is found in between 60 and 90% of people with OSAS and is the most common risk factor in adults. Smoking and alcohol have both been linked with a higher prevalence of snoring and sleep apnoea.
Some people are more likely to develop sleep apnoea because of their genes.
Sleep apnoea is more common in men than women.
Certain types of inherited facial bone structure are associated with a narrow throat and make OSAS more likely; the commonest is a receding chin. Specific genetic conditions such as Down syndrome also predispose the individual to OSAS.
OSAS also occurs in children and the commonest contributory factor is enlargement of the tonsils. In some children or adults severe congestion of the nose can make the condition worse.
Where relevant, lifestyle changes such as weight loss and reducing alcohol consumption and cigarette smoking can all help prevent the condition.
OSAS is often suspected from symptoms and clinical examination but in most cases overnight recording is needed for confirmation. A detailed sleep study, called polysomnography, records brain waves, muscle activity, eye movements, heart activity, chest movement, airflow at the nose and mouth and blood oxygen level (oximetry).
This detailed study is carried out in in a sleep clinic but with most individuals with suspected OSAS, simpler investigations can be performed using portable equipment, often in the patient’s home. Several devices are now available to record various combinations of blood oxygen levels, chest movement, airflow and heart rate.
The level of daytime sleepiness is assessed by a simple questionnaire called the Epworth Sleepiness Scale. This asks the individual to grade the likelihood of falling asleep in different everyday situations. Symptoms of sleep apnoea such as snoring and witnessed apnoeas are also likely to be reported by a bed partner.
The most effective treatment for sleep apnoea is continuous positive airway pressure (CPAP), which is simple and highly cost effective. This form of treatment involves a machine which generates a flow of air via a mask over the nose (or nose and mouth) at a pressure which is adjusted to keep the throat open during the night. For continuing benefit it needs to be used every night. Other options include a device worn inside the mouth to bring the lower jaw forward or, where relevant, surgery to remove the tonsils.
There are currently no drug treatments.