Obstructive sleep apnea is diagnosed when loud snoring is interrupted by episodes of completely obstructed breathing. This condition can be serious and sometimes fatal if not treated. The cumulative effects of these obstructed breathing episodes is reduced blood oxygen levels to the brain, forcing the patient to stay in a lighter sleep stage and preventing them from getting the rest benefit only achieved by a deeper sleep. This can lead to a tendency to fall asleep during daytime hours, on the job, or worse, at the wheel of a car. Also, over time the heart needs to work harder and other body systems are affected by sleep apnea.