Comparison of autonomic withdrawal in men with obstructive sleep apnea syndrome, systemic hypertension, and neither condition

Obstructive sleep apnea syndrome is characterized by obesity, nocturnal bre athing abnormalities, arterial hypertension, and an increased number of car diovascular events. Sympathetic activity is increased during nocturnal apne ic episodes, which may mediate the cardiovascular complications of sleep ap nea. We studied 15 male subjects with obstructive sleep apnea syndrome and associated hypertension, 54 subjects with mild to moderate essential hypert ension, and 25 healthy normotensive men. Cardiovascular autonomic control w as assessed using frequency domain measures of heart rate variability (HRV) during a controlled breathing test and during orthostatic maneuver. Compar ed with normotensive and hypertensive groups, total power and low- and high -frequency components of HRV during controlled breathing were significantly (analysis of variance, p <0.0001) lower in the obstructive sleep apnea syn drome. During the orthostatic maneuver, the change in total power of HRV wa s different between the 3 groups (analysis of variance, p = 0.004). The tot al power of HRV tended to increase in the normotensive (4.11 +/- 12.29 ms(2 )) and in hypertensive (2.31 +/- 12.65 ms(2)) groups, but decreased (1.13 /- 1.23 ms(2)) in the hypertensive group with obstructive sleep apnea syndr ome. According to multivariate regression analysis, age and sleep apnea wer e the major independent determinants of HRV. This study found that an abnor mal response to autonomic nervous tests characterizes hypertension in overw eight subjects with obstructive sleep apnea syndrome. This could be due to autonomic withdrawal or supersaturation of the end-organ receptors by exces sive and prolonged sympathetic stimulation. Our results also show the reduc ed response of orthostatic maneuver and controlled breathing in the hyperte nsive group compared with the normotensive group. (C) 2000 by Excerpta Medi ca, Inc.