Stressed and sleepless, many Americans spend their nights tossing and turning in the dark.  According to the National Sleep Foundation, a third of adults in the United States sleep less than 6.5 hours per night.  While most people experience occasional insomnia, a deadly condition called sleep apnea affects an estimated 20 million Americans.  Sleep apnea is also associated with cardiovascular diseases like high blood pressure, heart attack, congestive heart failure, cardiac arrhythmias and stroke.  Most sufferers are unaware that their restless nights are filled with the noisy signals of a sleep disorder-snoring, choking or gasping-that they forget completely on awakening.  Left untreated, obstructive sleep apnea can lead to serious health consequences, including fatigue-related accidents, heart disease, hypertension and diabetes.