Impaired autonomic balance during sleep in obstructive sleep apnea: origin or result

The ECG may be used as a means to uncover information on the function of organs and systems apart from the heart itself. We studied the autonomic function in adult patients with obstructive sleep apnea syndrome (OSAS) and expected their autonomic balance to be shifted towards sympathetic predominance. The study included 12 OSAS patients and 12 subjects with no respiratory disturbance during sleep, as diagnosed by attended whole-night polysomnography (PSG) and scored according to standard criteria. The time-frequency decomposition of beat-to-beat heart rate variability (HRV), detected from the ECG, served to evaluate autonomic function. The results showed an overall increased sympathetic activity during sleep and sympathetic predominance during slow-wave sleep (SWS) in patients, as compared to control subjects. The degree of sympathetic predominance correlated well with the severity of sleep apnea.