Sleep disordered breathing (SDB), expressed most frequently as obstructive sleep apnea (OSA), is a common syndrome, and becomes progressively more prevalent with increasing age . For the past several decades, a number of cross-sectional studies performed primarily in relatively small clinical cohorts or using surrogates such as snoring as markers of SDB have reported linkages between SDB and cardiovascular disease (CVD). For example, a high prevalence of OSA has been observed in patients with hypertension . Conversely, hypertension is found in a large percentage of OSA patients. With respect to cardiac disease, early studies linked OSA to ischemic heart disease [3, 4]. In addition, it has been shown that OSA is associated with deteriorations in left ventricular function  and that treatment of OSA with continuous positive airway pressure (CPAP) improves cardiac function. If SDB plays a causal role in the pathogenesis of CVD, increases in mortality would be expected among individuals with OSA. This hypothesis was supported in some [6, 7], but not all  retrospective studies. Whether or not SDB is an independent risk factor for CVD is an important public health question. According to the 1999–2000 National Health and Nutrition Examination Survey (NHANES), the prevalence of hypertension in the United States in those over age 55 years is 48% . According to the year 2000 census, there are ~59 million Americans age 55 or older. As previously noted, if 25–50% of these individuals also have OSA, then ~14.5–29 million people in the United States in this age category are at increased risk for CVD or excess mortality related to OSA.
In the past several years, a persuasive body of data now indicates a causal association, independent of obesity, between SDB and cardiovascular disorders such as hypertension, coronary artery disease (CAD), arrhythmias, congestive heart failure (CHF), and stroke. The association is strongest and most consistent between obstructive sleep apnea and hypertension. This review will summarize the most important studies demonstrating the linkages between SDB and cardiovascular disease, and outline potential responsible mechanisms.