Obstructive sleep apnea and heart rate variability in male patients with metabolic syndrome: cross-sectional study

Obstructive sleep apnea (OSA) is often accompanied by the metabolic syndrome. Because both conditions are associated with depressed heart rate variability (HRV) separately, our aim was to study whether co-morbid OSA is associated with more reduced HRV in male patients with the metabolic syndrome. In this cross-sectional study, 35 men (age, 57±11 years) with the metabolic syndrome (according to International Diabetes Federation criteria) were included. OSA severity was defined by the apnea-hypopnea index (AHI). HRV was assessed by 24-hr ambulatory electrocardiographic monitoring. Standard deviation of all normal-to-normal RR intervals (SDNN), the high frequency power (HFP), and the ratio of low- to high-frequency power (LF/HF) were measured. There were 14, 6, and 8 cases of severe (AHI ≥30/hr), moderate (15/hr≤AHI