Sleep-disordered Breathing and Snoring

Sleep-disordered breathing refers to a spectrum of conditions characterised by abnormal breathing during sleep. This can range from mild simple snoring to Obstructive Sleep Apnoea (OSA).

In simple snoring, there is mild narrowing of the upper airways causing noisy breathing during sleep but no associated sleep disturbance or impairment of daytime function.

In contrast, patients with OSA have more severe airway obstruction during sleep which results in significant sleep disturbance, repeated cycles of low oxygenation and impairment of daytime function.

In a local study, approximately 24 percent of adults are loud habitual snorers and about 15 percent of adults are estimated to have OSA (Puvanendran K et al, Sleep Research Online 1999).

Snoring is caused by the vibration or flapping of tissues lining the upper air passages. This may be due to:

• Relaxation of muscles causing the walls of the upper airway to fall together, causing them to vibrate.
• Swelling of the tissue in the walls, for example, due to anatomical or injury may cause narrowing.
• The tongue falls back into the throat when sleeping on the back, contributing to the snoring.
• Nasal blockage such as nasal allergy or deformities of the nasal septum (the cartilage partition between the two sides of the nose) can cause poor nasal airflow and set the soft tissues of the palate (roof of the mouth) and throat vibrating.

Individuals with OSA have a narrower and more collapsible upper airway causing repeated upper airway obstruction during sleep. When breathing stops, the level of oxygen in the bloodstream falls. The brain senses this decrease in oxygen and rouses the person from sleep. With awakening, the muscles at the back of the throat become more active and hold the airway open so that breathing can resume.