Patients with obstructive sleep apnea syndrome have permanent variations of their hemodynamic parameters during the night : heart rate, arterial blood pressure, cardiac output. This is due to the repetition of respiratory events (obstructive apnea and hypopnea) leading to frequent micro-arousals. These disorders have several consequences : hypertension, NO-dependent vasodilatation impairment, baroreceptor reflex impairment, insulin resistance and other cardiovascular impairments.

Objective of the study is to characterize the cardiovascular phenotype of patients with obstructive sleep apnea syndrome, relative to the presence of hypertension or not. Hypertension should not have been previously treated. 2 groups of apneic patients (SAS+HTA+ and SAS+HTA-) will be compared together, referred to group of non apneic but hypertensive patients (SAS-HTA+) and non apneic / non hypertensive patients (SAS-HTA-).

Apneic and hypertensive patients may have a sympathetic nervous system activation and a much more important vascular and baroreceptor reflex impairment, than non apneic but hypertensive patients.

During the study, a second visit as control will be done for apneic patients only, 3 to 6 months after SAS treatment setting.

Inclusion Criteria:

• patients with or without obstructive sleep apnea syndrome (AHI > 15)
• patients with or without hypertension

Exclusion Criteria:

• known or expected secondary hypertension
• pathologies with consequences on arterial blood pressure regulation: Parkinson's disease, patients with renal or cardiac graft, severe heart failure
• drugs with consequences on arterial blood pressure regulation : vasoconstrictors, vasodilatators, béta-agonists, antagonists, nitrites, theophylline, dipyridamol, sildenafil, immunosuppressors, IMAO, neuroleptics, tricyclic antidepressants, corticoids or long-term oral (>10 days) non steroidal anti-inflammatory drugs, oestroprogestative treatments
• atrial fibrillation, frequent extrasystoles (> or = to 10/minute)
• bedridden patients
• night shift workers
• surgical or carotid stenting history
• subjects unwilling or unable to provide written, signed and dated informed consent
• patient previously treated for obstructive sleep apnea syndrome (positive airway pressure, forward mandible prosthesis, maxillofacial surgery