ABSTRACT
BACKGROUND: Recent studies reported that untreated patients with obstructive sleep apnea syndrome had high long-term mortality rates, and cardiovascular complications of these patients had a major effect on mortality. Several data indicates that obstructive sleep apnea syndrome contributes to the development of diurnal systemic hypertension. But the pathophysiological mechanism of the development of systemic hypertension in these patients is still uncertain. This study was performed to evaluate the possible role of sympathetic nervous system activity for the development of systemic hypertension in patients with obstructive sleep apnea syndrome. METHOD: 35 patients with obstructive sleep apnea syndrome(OSAS) and 13 control subjects (Control) were included in this study. 21 patients of OSAS were normotensives(OSAS-NBP), and 14 patients of OSAS were hypertensives(OSAS-HBP). Full night polysomnography was undertaken to all subjects. We measured plasma norepinephrine(NE) and epinephrine(EP) concentrations during waking and sleep, using high performance liquid chromatography, in all patients and control subjects. RESULTS: In OSAS, OSAS-NBP and Control, plasma NE and EP concentrations during sleep were lower than during waking(p<0.01). But, in OSAS-HBP, there was no difference between during waking and sleep. Plasma NE concentrations during sleep of OSAS, OSAS-NBP and OSAS-HBP were higher than Control(p<0.05). In OSAS-HBP, daytime systolic blood pressure correlated with plasma NE concentration during sleep(r=0.7415, p<0.01), and correlated inversely with mean arterial oxygen saturation(r=-0.6465, p<0.05) or arterial oxygen saturation nadir(r=-0.6114, p<0.05) during sleep. CONCLUSION: The sympathetic activity during sleep of obstructive sleep apnea syndrome patients was higher than control subjects. In obstructive sleep apnea syndrome patients with systemic hypertension, there was no diurnal variation of sympathetic activity, and there was correlation between daytime systolic blood pressure and sympathetic activity during sleep. These data suggests that chronic hyperactivity of sympathetic nervous system may contribute to the development of diurnal systemic hypertension in patients with obstructive sleep apnea syndrome.