Autonomic activity difference during continuous positive airway pressure titration in patients with obstructive sleep apnea/hypopnea syndrome with or without hypertension

Background: Current evidence suggests that obstructive sleep apnea-hypopnea syndrome (OSAHS) is an independent risk factor for systemic hypertension. The mechanisms linking OSAHS to hypertension remain unclear. However, recent studies have indicated that abnormal autonomic control may be an important factor. Our study aims to evaulate differences in autonomic activity between hypertensive and normotensive OSAHS patients before and during continuous positive airway pressure (CPAP) therapy. Methods: Fifty-three OSAHS patients were analyzed in this study. Patients were divided into 2 groups, one group comprising patients with hypertension and the other of patients without hypertension. Heart rate variability (HRV) was assessed by polysomnography, before patients received CPAP titration and during CPAP titration. Then, HRV was compared between the hypertensive and normotensive groups. Multivarate analyses were used to evaluate the influence of clinical variables on autonomic activity. Results: Although HRV before CPAP titration was not statistically different between the 2 groups, low frequency variability was significantly lower in hypertensive subjects who received CPAP titration compared with normotensive subjects. Multivariate analysis revealed that hypertension is a determinant factor of autonomic change during CPAP use. Conclusions: Our findings demonstrate that CPAP therapy results in a greater and immediate change in autonomic activity in hypertensive OSAHS patients compared with normotensive OSAHS patients. This suggests that CPAP lowers blood pressure by decreasing the patient's autonomic activity.