PP.37.06

Abstract

Objective: Normal diurnal variation of both peripheral and central blood pressure (BP) in healthy subjects is characterized by the increase from morning to evening and nocturnal dipping. Obstructive sleep apnea (OSA) is commonly associated with the inverse 24-hour BP profile and nocturnal and morning BP elevation. However, the diurnal changes of central BP and arterial stiffness are not well investigated. Thus, we conducted a pilot study to assess the evening-to-morning variation of central BP and arterial stiffness in hypertensive patients with moderate-severe OSA. Design and method: Eighteen hypertensive patients (15 males, mean age 53.7 ± 12.0 years old) with moderate-severe OSA [median apnea-hypopnea index (AHI) 65.4 (17.4–115.0) episodes/hour] verified by full polysomnography (Embla, Natus, USA). The patients were overweight or obese [body mass index (BMI) 37.7 ± 4.9 kg/m2), and did not have concomitant cardiovascular diseases. All subjects underwent applanation tonometry (Sphygmocor, Australia) in the morning after awakening and in the evening before going to bed at night in sleep laboratory. Results: OSA patients had higher morning central diastolic BP (91.0 ± 8.1 vs. 86.4 ± 11.6 mmHg; p = 0,040) along with higher morning “office” peripheral diastolic BP (90.0 ± 8.1 vs. 85.1 ± 11.8; p = 0.024) compared to the evening values. Augmentation index (AI) was also slightly higher in the morning [26.1 (2.0; 53.0) vs. 17.0(−4; 35)%; p = 0.05]. Central systolic BP and pulse wave velocity (PWV) did not change significantly from evening to morning (p > 0.05). Correlation analysis showed a moderate association between evening central diastolic BP and AHI (rs = 0.56;p = 0.038) as well as with desaturation index (rs = 0.60;p = 0.023) that weakened after adjustment for age, BMI, peripheral BP, prescribed antihypertensive therapy. An inverse strong association between evening PWV and nocturnal O2 saturation level (rs = −0.81;p = 0.003) remained significant after adjustment for possible confounders. However, the morning parameters were not associated with OSA severity but only with confounding factors (age, “office” BP, therapy). Conclusions: The pilot study demonstrated an inverse diurnal variation of central diastolic BP and arterial stiffness (AI) in hypertensive patients with moderate-to-severe OSA that corresponds to the common impairment of 24-hour ambulatory BP profile in these patients. The role of sleep apnea per se requires further investigation in a controlled study.