The result of stop breathing (apnea) is reducing levels of oxygen and increasing levels of carbon dioxide. The reduction in oxygen and increase in carbon dioxide can alert the brain to resume breathing and cause an arousal (waking up from sleep). During each arousal, a signal is sent from the brain to the upper airway muscles, to open the airway and breathing can be resumed. It is often associated with a loud snort or gasp. These frequent arousals prevent the patient from getting enough restorative, deep sleep.

Because of the serious disturbances of normal sleep, sufferers of sleep apnea often feel very sleepy during the day. It affects their concentration and daytime performance.

The consequences of sleep apnea range from annoying to life-threatening. Here is an abbreviated list of effects of sleep apnea: