Sleep-Disordered Breathing and Cardiovascular Disease

Sleep apnea is defined as repetitive episodes of decreased or total cessation of respiratory airflow during sleep, leading to a fall in oxygen saturation of 4% and sleep fragmentation. Sleep apnea can be central or obstructive. Central sleep apnea (CSA) is characterized by apneas secondary to diminution or cessation of thoraco-abdominal respiratory movements (due to dysfunction of central respiratory control mechanisms). Obstructive sleep apnea (OSA) is caused by upper airway collapse during inspiration and is accompanied by strenuous breathing efforts. When defined as 5 episodes of apnea or hypopnea per hour of sleep, OSA is relatively common, affecting 24% and 9% of middleaged men and women, respectively.1 CSA is primarily seen in patients with congestive heart failure (CHF), although it occasionally may occur in healthy normal subjects, in people at high altitudes, and in association with central neural lesions. Sleep apnea constitutes a major public health problem because of its high prevalence and its emerging association with cardiovascular morbidity.