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Background and Objectives: Whether obstructive sleep apnea (OSA) is associated with abnormal function of autonomic nervous system is still debatable. The purpose of this study was to evaluate the presence of autonomic modulation using heart rate variability (HRV) in both male and female OSA patients.
Methods: Eighteen untreated moderate to severe OSA patients aged between 30 to 70 years old and 18 gender- and age-matched non-OSA patients were studied. HRV was analyzed at rest and a 70o head-up tilt.
Results: Body mass index was higher (p<0.05) and mean oxygen saturation (%) was lower (p<0.05) in OSA patients. Although the mean AHI was 17.8 ± 3.7 events/hour which is indicative of moderate OSA, the arousal index of 32.0 ± 9.7 events/hour signifies severe OSA. Non-OSA and OSA patients were comparable for HF whereas OSA patients exhibited significant increased SDNN and LF/HF ratio (p<0.05) and decreased RMSSD (p<0.001) in either supine or 70o head-up tilt positions. Furthermore, LF was significantly greater in a tilt position in OSA compared to non-OSA patients. In comparison with supine, the tilt position showed significant increased LF (p<0.001) and LF/HF ratio (p<0.001), and decreased HF (p<0.001) in the non-OSA group while significant increased SDNN (p<0.05), LF (p<0.001) and LF/HF ratio (p<0.001) were observed in the OSA group. Nevertheless, LF/HF ratio were greater in the OSA compared to that of the non-OSA group in a head-up tilt (2.6 ± 1.1 vs. 1.5 ± 0.4) (p<0.001).
Conclusion: Our findings demonstrate that cardiac autonomic control may be attenuated by OSA.