Obstructive sleep apnea is the most common sleep apnea diagnosis. This disorder is caused when soft tissue in the back of your throat relaxes during sleep and blocks your airway. As airflow stops, the oxygen level in your blood drops, causing your brain to kick start the breathing process, which is often accompanied by gasps or choking. Sleep apnea causes your sleep cycle to reset multiple times during night, which not only affects how you feel when you wake up, but can also lead to chronic conditions and can even be fatal if the case is severe and left untreated.