While you sleep, all your muscles relax, including those controlling your airway. Sleep apnea can cause your airway to collapse and restrict airflow by 80% or more. In some people, these interruptions to breathing can occur as frequently as 30 or more times within an hour, sometimes lasting ten seconds or longer. ​ When your breathing is obstructed, your tissues are not able to receive adequate oxygen. Your brain tells your body to breathe, which can cause you to wake up gasping for air. As this cycle repeats throughout the night, you may often wake feeling as though you have had little or no sleep.