Objective: Heart rate power spectral analysis (HRPSA) can provide information of sympathetic and vagus activities. The aim of the study was to investigate nocturnal variations of autonomic nervous system (ANS) before and during continuous positive airway pressure (CPAP) treatment in patients with OSA.
Method: 56 subjects with severe OSA were recruited to undergo 7-hour nocturnal polysomnography and ECG monitoring in sleep lab before and during CPAP treatment. 30 subjects without OSA were included as controls. Subjects were excluded if they were receiving medications known to influence ANS activities. ANS was evaluated by HRPSA.
Result: In addition to repeated sleep apneas and oxygen desaturations, mean areas of LF (1 383 +/- 305) and HF (662 +/- 190) in OSA subjects were significantly higher than those in the controls (LF 125 +/- 64, P < 0.001; HF 163 +/- 78, P < 0.001). With effective CPAP treatment, LF (221 +/- 81) and HF (221 +/- 108) decreased remarkably (P < 0.001, separately) and reached the levels of controls (P > 0.05, separately).
Conclusion: The results suggested that nocturnal ANS activities are abnormal in patients with OSA, especially the enhancement of sympathetic nervous activity. Fluctuation of ANS induced by apnea and oxygen desaturation may explain the association between OSA and cardiovascular diseases. CPAP treatment is effective in improving ANS activities by way of eliminating apnea and reversing hypoxemia.