Objective To study the effects of obstructive sleep apneas on endothelial function and autonomic modulation. Methods From June 2009 to June 2011, male patients with obstructive sleep apnea hypopnea syndrome (OSAHS) were consecutively enrolled in this study. Patients with an apnea/hypopnea index (AHI) of greater than 15 and without previous treatment for OSAHS were included as Group OSAHS and obese subjects with an AHI of less than 5 were included as non-OSAHS controls (Group Control). Electrocardiography and beat-to-beat blood pressure were continuously recorded from the radial artery by applanation tonometry which was synchronized with polysomnography recording. Endothelial function was measured by arterial augmentation index (AAI). Spectral analysis of heart rate variability (HRV) and blood pressure variability (BPV) were computed for cardiac parasympathetic modulation (high frequency power, HF); sympathetic modulation (low frequency power, LF), sympathovagal balance (LF/HF power of R-R variability, LF/HF) and BPV sympathetic modulation (BPV LF) in normalized units [total power of the components/(total power-very LF power)×100]. Results Finally, 27 moderate-severe OSAHS patients and 22 non-OSAHS obese controls were recruited in the Group OSAHS and Group Control, respectively. In Group OSAHS, the age was 43.3±9.3 year-old, body mass index (BMI) was 36.8±8.7 kg/m 2 ; in Group Control, the age was 42.9±8.6 year-old, BMI was 34.4±7.9 kg/m 2 ; there were no significant differences in age and BMI between the Group OSAHS and Group Control (all P>0.05). The baseline AAI (12.5%±2.2% vs. 8.2%±2.1%) and BPV LF (68.3%±13.5% vs. 61.1%±11.7%) of the Group OSAHS were significantly higher than those of the Group Control (all P<0.05). And after overnight sleep, systolic BP (143.7±14.2 vs. 132.8±13.3 mm Hg), diastolic BP (87.7±7.7 vs. 78.6±5.5 mm Hg), HRV LF (69.7%±14.4% vs. 64.3%±12.1%), HRV LF/HF (3.7±2.0 vs. 2.3±1.3) and BPV LF (77.8%±15.6% vs. 68.3%±13.5%) of the Group OSAHS were significantly increased (a
