The primary objective of this study is to observe if Sibutramine is effective in improving the symptoms and signs of sleep apnea in obese patients. The secondary objectives are to document the effects of Sibutramine on heart rate variability and 24-h arterial pressure values. We hypothesized that sibutramine will improve sleep disordered breathing, cardiac autonomic function and systemic blood pressure in obese patients with obstructive sleep apnea (OSA).