Obstructive sleep apnea is diagnosed when loud snoring is interrupted by episodes of partially or completely obstructed breathing. This condition can be serious and sometimes fatal if these episodes last over ten seconds and occur more than five times an hour. The effect of these obstructed breathing episodes is reduced blood oxygen levels to the brain, forcing the snorer to awaken momentarily many times and stay in a lighter sleep stage. This prevents the snorer from obtaining the rest benefit achieved only during deeper, consolidated sleep, and can lead to a tendency to fall asleep during daytime hours - on the job, or worse at the wheel of a car. After many years with the disorder, elevated blood pressure and heart enlargement may occur.