Any condition that contributes to the narrowing at the back of the throat such as enlarged tonsils or adenoids favour the development of OSA.
Large tonsils are the most common cause of snoring and sleep apnoea in infants. They can also be the occasional cause of problems in adults although nasal and soft palate problems are the more common causes of adult snoring.
Other factors which may influence the snoring condition and the development of OSA are obesity, ageing and associated loss of general muscle tone, throat congestion due to reflux of stomach acid (heartburn); and the effects of alcohol, sedatives and smoking.
In obesity, excessive fat accumulation in the upper airway may amplify an existing anatomic narrowing of the upper airway that was causing minimal obstruction previously.
Snoring and OSA are also more common among males and in individuals with a genetic predisposition leading to facial and jaw abnormalities.