The aim of this prospective single-center study is to evaluate sympathetic nervous system directly measured by microneurography, 24-hour blood pressure, endothelial function, vascular compliance, quality of life and platelet adhesion in patients with sleep apnea syndrome (defined by a complaint of excessive daytime sleepiness, an Epworth sleepiness score>8[10], and an apnea/hypopnea index (AHI>15/h) before and after catheter-based radiofrequency ablation of renal nerve. If the selected patients are treated with CPAP, this therapy should be stable during the whole study time. Primary and secondary end-point will be measured before and 1, 3, 6 and 12 months after renal sympathetic denervation.