If you suffer from this type of sleep apnea, brief episodes of obstructed breathing can occur hundreds of times each night, lasting 20 seconds or longer. During one of these episodes, you breathe and snore while your muscles gradually relax until airflow is completely or almost completely obstructed. Your brain senses a decrease in oxygen and briefly rouses you from sleep. Your muscles "awake" and reopen the airway, usually with a gasp or snort. Afterward, you quickly fall asleep again, and the pattern is repeated. During each of these breathless periods, the level of oxygen in the blood falls to dangerously low levels, raising blood pressure and putting a strain on the cardiovascular system.

These repeated awakenings prevent restful and refreshing sleep. As a result, one of the key symptoms of sleep apnea is excessive daytime sleepiness which can result in lower on-the-job productivity and greater tendency to have accidents. For example, studies have shown that people with sleep apnea are three to five times more likely to have automobile accidents than the general population.