" Obstructive sleep apnea"(OSA) is a sleep breathing disorder. When a person with OSA tries to sleep the back of the throat closes and blocks the flow of air into lungs.When this happens, a person's sleep is disrupted, causing minor awakenings(which the individual may not recognize). This occurs many times throughout the night, causing poor sleep quality,excessive daytime sleepiness, poor concentration, and sometimes depression.It is possible that poor outcomes observed in stroke patients with OSA result from these neurocognitive phenomena, presumably by reducing effective participation in rehabilitation activities.OSA is treated with nasal continuous positive airway pressure(CPAP).CPAP therapy keeps the back of the throat open so that airflow is never blocked.The study is designed to investigate whether treatment of OSA with CPAP improves the results of rehabilitation.