Untreated obstructive sleep apnea is one of the leading causes of excessive daytime sleepiness. Obstructive sleep apnea is defined as episodes of apneas (not breathing) which last more than 10 seconds and that occur during sleep. These episodes may occur hundreds of times per night and can lead to fragmented sleep. During these events, the individual’s oxygen level can fall to dangerously low levels (hypoxemia) and may result in cardiac arrhythmias (irregular heartbeats), which can at times be fatal. Also, individuals with obstructive sleep apnea are far more prone to heart attacks and strokes.