Sleep-disordered breathing (SDB) refers to a group of conditions where breathing is interrupted or becomes shallow during sleep. The most common type of SDB is obstructive sleep apnoea (OSA), which refers to when the upper airway collapses or becomes blocked repeatedly, causing breathing to stop for short periods during sleep (Fig. 108.1). Snoring is the sound that occurs during sleep due to the throat vibrating as air tries to pass through to the lungs. Beyond SDB, other types of sleep disorders fall into broad categories of (i) lack of sleep (e.g. insomnia), (ii) circadian rhythm disorders, which are related to dysfunction of the biological clock (e.g. jet lag), (iii) movement disorders (e.g. restless leg syndrome), (iv) parasomnias (e.g. sleepwalking) and (v) too much sleep (e.g. narcolepsy).