Obstructive Sleep Apnoea is a serious, potentially life-threatening condition that is far more common than is generally understood. Obstructive Sleep Apnoea is a breathing disorder characterised by brief interruptions of breathing during sleep. It owes its name to a Greek word, apnoea, meaning "without breath".

The effects of OSA is that a person can stop breathing for periods when asleep. These interruptions (apnoeas), which last for 10 seconds or more, occur when the airway narrows so much that it closes. This stops breathing, and the brain reacts by briefly waking the subject, causing the airways to re-open and breathing to restart. The individual is usually unaware of this awakening and this process can be repeated up to several hundred times during the night.

Proper restful sleep becomes impossible, resulting in sleepiness and impairment of daytime function. Early recognition and treatment of OSA is important. The excessive sleepiness associated with OSA impairs quality of life and places people at increased risk of road traffic and other accidents. It may also be associated with irregular heartbeat, high blood pressure, heart attack and stroke.

• "Apnoea" is a Greek word meaning "without breath." An apnoea is clinically defined as a cessation of breath that lasts at least ten seconds.
  
  
• "Hypopnea" also comes from Greek: "hypo" meaning "beneath" or "less than normal" and "pnoea" meaning "breath." A hypopnoea is not a complete cessation of breath but can be defined as a perceptible reduction in airflow that leads to sleep fragmentation or to a decrease in the oxygen level in the bloodstream.
  
  
• The apnoea-hypopnoea index (AHI) or respiratory disturbance index (RDI) refers to the total number of apnoeas and hypopneas divided by the total sleep study in a patient’s sleep study. The AHI gives one measure of the severity of the sleep apnoea.
  
  
• Typically the soft tissue in the rear of the throat collapses and closes the airway, forcing sufferers to stop breathing repeatedly during sleep, sometimes hundreds of times a night.
  
  
• Although the typical Obstructive Sleep Apnoea patent is overweight, male, and over the age of forty, sleep apnoea affects both males and females of all ages and those of ideal weight.

The most common symptoms of Obstructive Sleep Apnoea are loud snoring and excessive sleepiness (i.e., falling asleep easily and sometimes often inappropriately). Untreated Obstructive Sleep Apnoea can be life threatening; consequences may include high blood pressure and other cardiovascular complications.