It is defined as breathing arrest for at least 10 seconds repeatedly during sleep. There are two types of sleep apnea central and obstructive. Central sleep apnea is due to decrease in CNS thrive, this type is associated with aging, heart failure, or a stroke. Obstructive sleep apnea is due to physical airway obstruction, or may be caused by ↓ pharyngeal muscle tone, obese neck pressing on the upper airway, ↑ size of tonsils, or nasal septal deviation. Symptoms are chronic daytime sleepiness similar to narcolepsy, loud snoring, unrestful sleep, Physical exam shows large neck circumference, crowded oropharynx, or micrognathia. Treatment is by CPAP or surgery. Complications are Arrhythmia or Pulmonary hypertension.