 Most observational studies examined the effects of CPAP across a broad-range of OSA severity, and have included patients with and without the metabolic syndrome. Up to now, no study analyzed the effects of CPAP on glucose and lipid metabolism, systemic inflammation, oxidative stress, and the global cardiovascular disease CVD risk within the same cohort of subjects with severe OSA and concurrent metabolic syndrome. Importantly, the metabolic syndrome exacerbates CVD risk over and above that attributable to OSA alone. Therefore, reduction of CVD risk in patients with OSA and concurrent metabolic syndrome is of paramount importance. 