Performing a search in PubMed (search terms were “apnea,” “obstructive sleep apnea,” “sleep apnea syndromes,” “atherosclerosis,” “arteriosclerosis,” “intima-media thickness,” “plaque,” “catheterization,” “ultrasound,” “intravascular ultrasound,” and “coronary artery calcium”) for articles that evaluated atherosclerosis in patients with OSA (excluding studies that evaluated only endothelial function, arterial stiffness, and coronary flow), we found 36 studies from 1998 (the year of the first report of atherosclerosis in patients with OSA) to December 2010.51-84 The consistency of the data can be verified by the fact that 33 of the 36 studies found a positive association between markers of atherosclerosis (most in the carotid bed) and OSA. A major drawback of these numerous studies was that in a majority of research subjects, multiple proatherogenic factors coexisted with OSA. Therefore, the role of OSA in atherogenesis could not be established unequivocally. To avoid confounding factors associated with OSA, Drager et al60 examined a select group of young (<55 years) male OSA patients who were free of comorbidities and were on no medications. Compared with proper matched control subjects without OSA, patients with OSA had increased arterial stiffness and early signs of atherosclerosis, including increased carotid intima-media thickness. Moreover, the severity of all vascular abnormalities in patients with OSA correlated with the severity of OSA expressed by the apnea-hypopnea index and minimal nocturnal oxygen saturation. One limitation of this study is that these relatively young patients with OSA may not represent the typical patient with OSA. For instance, among patients with OSA, approximately 50% have hypertension, a well known risk factor for atherosclerosis.75 In addition, many patients with OSA present with masked hypertension, defined as normal clinical BP values (<140/90 mm Hg) but abnormal diurnal ambulatory BP monitoring (≥135 or ≥85 mm Hg).85 A subsequent study found that patients with OSA had similar signs of atherosclerosis to those with hypertension, and that patients with both conditions (ie, OSA and hypertension) showed additive effects on validated markers of atherosclerosis (Fig 3).75 More recently, Drager et al82 studied consecutive patients with metabolic syndrome, all of whom had risk factors for atherosclerosis. Interestingly, OSA was present in 63% and was independently associated with markers of atherosclerosis. Of note, all studied markers of atherosclerosis were similar in OSA patients with or without daytime sleepiness, suggesting that the harmful effects of OSA are not confined to individuals with hypersomnolence.82 Together, these results indicate that the atherosclerotic burden of OSA affects patients with and without comorbidities.