Obstructive sleep apnea (OSA) is a highly prevalent disease, affecting 4% of men and 2% of women. 1 Obstructive sleep apnea (OSA) is a common and frequently under diagnosed condition characterized by recurrent episodes of partial or complete obstruction of the upper airway during sleep, decrease in oxygen saturation and daytime somnolence. 2 Significant clinical consequences of OSA cover a wide spectrum including neurocognitive dysfunction 3 , cardiovascular disease (CVD), 4,5 metabolic dysfunction, 6,7 respiratory failure, and cor pulmonale. 8 OSA patients frequently have several risk factors for CVD development, such as obesity, hypertension, and diabetes. [4][5][6] These risk factors are entangled in such a way that it is difficult to isolate the relative contribution of OSA to cardiovascular risk. OSA is independently associated with several CVD, including hypertension, ischemic heart disease, atrial fibrillation, cerebrovascular disease, and heart failure, 4,5, though the magnitude of OSA effects, as compared to other risk factors for cardiovascular disease, is not well established. Pathophysiology of CVD:The pathophysiology of possible deleterious cardiovascular effects of OSA is thought to involve two major components: first, the mechanical effect of apneas on intrathoracic pressures and heart function and second intermittent hypoxemia resulting in sympathetic overdrive and endothelial cell dysfunction (figure1). 9 Although there is no definitive evidence to determine whether OSA directly causes cardiovascular disease, the available data do suggest an increased risk of having car E-mail : drmosharraf_hossain@yahoo.com AbstractObstructive sleep apnea (OSA) is the most common form of sleep-disordered breathing, affecting 5-15% of the population. It is characterized by intermittent episodes of partial or complete obstruction of the upper airway during sleep that disrupts normal ventilation and sleep architecture, and is typically associated with excessive daytime sleepiness, snoring, and witnessed apneas. Patients with obstructive sleep apnea present risk to the general public safety by causing 8-fold increase in vehicle accidents, and they may themselves also suffer from the physiologic consequences of OSA; these include hypertension, coronary artery disease, stroke, congestive heart failure, pulmonary hypertension, and cardiac arrhythmias. Of these possible cardiovascular consequences, the association between OSA and hypertension has been found to be the most convincing. Although the exact mechanism has not been understood, there is some evidence that OSA is associated with frequent apneas causing mechanical effects on intrathoracic pressure, cardiac function, and intermittent hypoxemia, which may in turn cause endothelial dysfunction and increase in sympathetic drive. Therapy with continuous positive airway pressure has been demonstrated to improve cardiopulmonary hemodynamics in patients with OSA and may reverse the endothelial cell dysfunction. Limited availability of diagnostic measures and unawaren...