Nocturnal Blood Pressure Variability in Patients with Obstructive Sleep Apnea Syndrome

Obstructive sleep apnea (OSA) is a common respiratory disorder associated with hypertension and cardiovascular complications. Blood pressure variability may be a sign of risk of cardiovascular events. The aim of this study was to investigate the hypothesis that severe OSA syndrome is associated with increased blood pressure variability. Based on respiratory polygraphy, 58 patients were categorized into two groups: severe OSA with apnea/hypopnea index (AHI) greater than 29 episodes per hour (mean 52.2 +/- 19.0/h) and mild-to-moderate OSA with AHI between 5 and 30 episodes per hour (mean 20.2 +/- 7.8/h). A 24-h noninvasive blood pressure monitoring was performed. The standard deviation of mean blood pressure was used as the indicator of blood pressure variability. In patients with severe, compared with mild-to-moderate OSA, a higher mean nocturnal systolic blood pressure (133.2 +/- 17.4 mmHg vs. 117.7 +/- 31.2 mmHg, p < 0.05) and diastolic blood pressure (80.9 +/- 13.1 mmHg vs. 73.8 +/- 9.2, p < 0.01), nocturnal systolic blood pressure variability (12.1 +/- 6.0 vs. 7.6 +/- 4.3, p < 0.01) and diastolic blood pressure variability (10.5 +/- 6.1 vs. 7.3 +/- 4.0 p < 0.05), nocturnal mean blood pressure variability (9.1 +/- 4.9 mmHg vs. 6.8 +/- 3.5 mmHg) were detected. The findings of the study point to increased nocturnal systolic and diastolic arterial blood pressure and blood pressure variability as risk factors of cardiovascular complications in patients with severe OSA.