Obstructive sleep apnea: implications for cardiac and vascular disease.

ALONG WITH THE EPIDEMIC OF obesity, there is a growing awareness of sleep-disordered breathing as a potential and treatable risk factor for cardiovascular disease. The repetitive nocturnal hypoxemia experienced by patients with obstructive sleep apnea (OSA) is associated with activation of a number of neural, humoral, thrombotic, metabolic, and inflammatory disease mechanisms, all of which have also been implicated in the pathophysiology of cardiac and vascular disease. Activation of these mechanisms is often evident even in patients with OSA who are free of overt cardiovascular disease, suggesting that OSA may conceivably contribute to the initiation and progression of cardiovascular disease (FIGURE 1). SleepapneacanbecategorizedasOSA, in which there is preserved and increased respiratory effort despite partial or complete occlusion of the upper airway; or as central sleep apnea (CSA), in which there is absence of both respiratory efforts and airflow. The apneahypopnea index (ie, the number of apneic and hypopneic events per hour) is used as one index of the presence and severity of sleep apnea. For OSA, an apnea-hypopnea index of 5 to 15 indicates mild apnea; of 15 to 30, moderate apnea; and of greater than 30, severe apnea. Approximately 1 in 5 adults has at least mild OSA (apnea-hypopnea index, 5-15), and 1 in 15 adults has at least moderate OSA (apnea-hypopnea index, 15-30). Other measures of the severity of sleep apnea include the severity of oxygen desaturation and the level of daytime sleepiness. Obstructive sleep apnea is commonly associated with obesity and also is often present in patients with