RESUMO
PURPOSE: Obstructive sleep apnea (OSA) is a risk factor for the development of hypertension and cardiovascular disease. Apnea overloads the autonomic cardiovascular control system and may influence blood pressure variability, a risk for vascular damage independent of blood pressure levels. This study investigates the hypothesis that blood pressure variability is associated with OSA. METHODS: In a cross-sectional study, 107 patients with hypertension underwent 24-h ambulatory blood pressure monitoring and level III polysomnography to detect sleep apnea. Pressure variability was assessed by the first derivative of blood pressure over time, the time rate index, and by the standard deviation of blood pressure measurements. The association between the apnea-hypopnea index and blood pressure variability was tested by univariate and multivariate methods. RESULTS: The 57 patients with apnea were older, had higher blood pressure, and had longer duration of hypertension than the 50 patients without apnea. Patients with apnea-hypopnea index (AHI) ≥ 10 had higher blood pressure variability assessed by the standard deviation than patients with AHI < 10 during sleep (10.4 ± 0.7 versus 8.0 ± 0.7, P = 0.02) after adjustment for age, body mass, and blood pressure. Blood pressure variability assessed by the time rate index presented a trend for association during sleep (P = 0.07). Daytime blood pressure variability was not associated with the severity of sleep apnea. CONCLUSION: Sleep apnea increases nighttime blood pressure variability in patients with hypertension and may be another pathway linking sleep abnormalities to cardiovascular disease.