Katie Says:

Causes of sleep apnoea:
During sleep the activity of the respiratory muscles is reduced, especially during REM* sleep. During this time the diaphragm can be the only muscle to maintain respiration. Particularly because of reduced muscle tone during sleep, obstructive sleep apnoea occurs because the airway at the back of the throat is sucked closed more easily, creating narrowing of the airway that can result in snoring. Usually people with obstructive sleep apnoea have an airway that is more narrow than normal.
*REM stands for 'rapid eye movement'. It is a stage of sleep that is characterized by rapid movements of the eye and low muscle tone. It occupies around 25% of sleep and we might have 4 or 5 periods of REM during one night.

Particular parts of the throat can cause trouble and increase risk:
Enlarged tonsils- eg tonsillitis
pharangeal soft tissue changes in **acromegaly or hypothyroidism
nasal obstruction- nasal deformities, rhinitis, polyps, adenoids
large tongue
normally narrow airway- eg obesity
certain shapes of palate and jaw
large neck
**Acromegaly is a hormonal disorder when the pituitary gland produces excess growth hormone


Lifestyle factors that make obstructive sleep apnoea worse:
overweight with lack of exercise contributing to this
COPD , for example as a consequence of smoking or occupational dust
sleeping on one's side instead of the back can make obstructive sleep apnoea worse in some people
Consumption of alcohol and sedatives before bedtime can reduce muscle tone due to a 'dampening effect' in the Central Nervous System, particularly within the respiratory centre in the Medulla



References:
Medline Plus Encyclopedia, "sleep apnoea"
http://www.nlm.nih.gov/medlineplus/ency/article/000811.htm
http://www.entcolumbia.org/osa.htm
Kumar and Clark, "obstructive sleep apnoea"
Talley and O'conner, "apnoea"