Inclusion Criteria:  Cases: patients with AHI > 30/h Controls: subjects with AHI < 5/h and Epworth <10  Exclusion Criteria:  Epworth>18 BMI<40Kg/M2 Arterial Hypertension Diabetes Mellitus Cerebrovascular disease Ischemic heart disease Cardiac arrhythmia Chronic cardiovascular diseases Daytime Oxygen saturation>95% Risk professions (professional drivers) Concomitant treatment with antihypertensives, statins, antidiabetics, beta- blockers or systemic corticosteroids. Pretreatment with CPAP. Participation in another clinical trial thirty days prior to randomization Abnormal values of a cognitive test.