Many potential mechanisms of atherosclerosis have been reported, but direct evidence for atherosclerosis is still lacking. Subjects with OSA also have comorbidities which may give rise to atherosclerosis. With the advancement of non-invasive techniques for detection of vascular endothelial damage and early atherosclerosis, it is possible to detect early vascular abnormalities in otherwise healthy OSA subjects. This hypothesis underlies our objectives to explore the relationship between AGE and the markers of endothelial dysfunction and early atherosclerosis. Some of these early changes, especially at endothelial level, may be reversible if the insult of OSA is removed. Thus a longitudinal comparison of OSA-treated and OSA-untreated subjects on such changes would further help to clarify the issue.