There are two main types of sleep apnoea – obstructive and central. Obstructive sleep apnoea (OSA) is the most common form and is sometimes known as the obstructive sleep apnoea/hypopnoea syndrome (OSAHS).
Obstructive sleep apnoea
In OSA the upper airway collapses intermittently and repeatedly during sleep. This collapse can be complete, with total obstruction of the airway passage and no respiratory airflow (apnoea), or partial, with reduction in breathing called hypopnoea. An apnoea usually lasts for at least ten seconds but may be much longer in some cases.
As the sufferer falls asleep the muscle tone in the upper airway decreases leading to narrowing of the passageway. This, in turn, produces an increase in breathing effort in an attempt to overcome this airway narrowing which then leads to a transient arousal from deep sleep to wakefulness or a lighter sleep phase. The patient then falls more deeply asleep again and the whole cycle repeats itself. This can occur many hundreds of times throughout the night leading to fragmentation of normal sleep architecture and a reduction in the quality of sleep with the generation of restless, disturbed and unsatisfying sleep. This in turn produces the symptoms of excessive daytime sleepiness, poor concentration and a reduction in alertness.
Sleep apnoea can be associated with:
- Tiredness and unrefreshing sleep
- Excessive daytime sleepiness especially when driving
- Poor concentration
- Witnessed apnoeas and choking episodes during sleep
- Restless sleep
- Irritability / personality change
- Reduced sex drive
- High blood pressure, stroke, heart disease and diabetes (see associated conditions)
- Sudden death (rare).
Your symptoms can be assessed by a careful history and by use of questionnaires such as the Epworth Sleepiness Score (ESS). A Score of >9 out of 24 may be associated with sleep apnoea and snoring, but sometimes people with lower scores have significant sleep apnoea.
Some patients with OSA will require treatment with a breathing machine at night called nasal-CPAP (continuous positive airways pressure).
Central Sleep Apnoea
Central sleep apnoea is much less common than OSA and is due to failure of the brain to send adequate impulses to the breathing muscles, predominantly the diaphragm. This can sometimes be an indication of a brain disorder such as a previous stroke, or is seen sometimes in association with some heart diseases.
Obstructive Sleep Apnoea (OSA) has been linked with the following medical conditions:
- High blood pressure (hypertension)
- Heart disease and heart attacks (cardiovascular disease)
- Heart rhythm disorders (arrhythmias)
- Driving accidents
- Thyroid and some endocrine disorders
- Risk of stroke.
In many of these cases, it is clear that these conditions are linked directly by the OSA and may also be due to an underlying cause of the OSA itself, such as obesity.
If appropriate, your sleep study will help to establish whether you have sleep apnoea, snoring or both, and will guide decisions about treatment options.