Apnoea is Greek for “without breath”. Sleep apnoea is characterised by apnoea episodes that occur while a patient sleeps. There are two main types of sleep apnoea: obstructive and central apnoea. The most common type of apnoea is obstructive. Some people, however, could suffer from both types simultaneously, and this is referred to as mixed sleep apnoea.
Obstructive sleep apnoea
With obstructive sleep apnoea (OSA), cessation of airflow during sleep is caused by a decrease in the tone of the muscles supporting the airway. This results in an obstruction such as partial or complete closure of the pharynx and prevents air from entering the lungs. Complete closure (obstruction) stops airflow (apnoea), whereas partial obstruction decreases airflow (hypopnoea).
Obstruction of the airway
These non-breathing stops can be very short, but could also last up to two minutes. They become clinically significant if the cessation lasts for more than ten seconds each time and occurs more than ten times per hour. The frequency of the episodes can be up to 30 times an hour or more, heavily interrupting a person’s sleep time.
With each apnoea during sleep, the brain receives a signal to arouse the individual from sleep in order to resume breathing, and consequently sleep is extremely fragmented. People with untreated sleep apnoea are generally not even aware of the awakenings but only of being sleepy during the day. They may, however, realise that they snore or gasp for air during sleep. Loud snoring, punctuated with periods of silence (apnoeas) is typical but not always present.
Moderate to severe sleep apnoea can be diagnosed from the patient history and a sleep study using oximetry or other monitoring devices carried out in the person’s home. In some cases, further studies that monitor additional physiological variables in a sleep laboratory or at home may be required, especially when alternative diagnoses are being considered. The severity of sleep apnoea is usually assessed on the basis of both severity of symptoms (particularly the degree of sleepiness) and the sleep study, by using either the Apnoea/Hypopnoea Index (AHI) or the oxygen desaturation index.
Sleep apnoea is very common, although still very underdiagnosed. It is estimated that up to 2% of women and 4% of men in the world suffer from this condition1. Risk factors for sleep apnoea include a family history of sleep apnoea, excess weight, a large neck, a recessed chin, abnormalities in the structure of the upper airway, smoking and alcohol consumption. The typical referred patient is male, seriously overweight and over the age of forty. However, sleep apnoea can affect both males and females of all ages and any weight.
1 Young T. The occurrence of sleep-disordered breathing among middle-aged adults. N Engl J Med 1993; 328(17):1230-1235.