Mechanical and structural problems in the airway can cause interruptions of breathing during sleep. In some people, apnea occurs during the throat muscles and tongue relax in sleep and it partially block the opening of the airway.

When the muscles of the soft palate at the base of the tongue and the uvula (the small fleshy tissue hanging from the center of the back of the throat) relax and sag, the airway becomes blocked. It makes the breathing laborious and noisy. Sometimes, it just stopped altogether.

Sleep apnea also can occur in obese people who has excessive amount of tissue in the airway and makes it narrowed. The narrowed airway makes the air cannot easily flow into or out through the airway. This results in heavy snoring, periods of no breathing, and frequent arousals causing abrupt changes from deep sleep to light sleep. All these is unknown to the patients with sleep apnea. The condition can be aggregated by ingestion of alcohol and sleeping pills.