Middle-aged and older, obese men seem to be at higher risk, though as many as 40% of people with obstructive sleep apnoea are not obese. Anatomical factors such as nasal obstruction, a large tongue, a narrow airway and certain shapes of the palate and jaw also increases the likelihood of sleep apnoea. A large neck or collar size is strongly associated with obstructive sleep apnoea. Ingestion of alcohol before sleep or sleeping pills may also predispose to episodes of apnoea.