Concomitant existence and interaction of cardiovascular abnormalities in obstructive sleep apnea subjects with normal clinic blood pressure.

This study was conducted to examine the existence of increased arterial stiffness of the central to middle-sized arteries and left ventricular (LV) structural/functional abnormalities in subjects with obstructive sleep apnea (OSA) who had normal clinic blood pressure. Brachial-ankle pulse wave velocity (baPWV) measurement and echocardiography were conducted in 164 consecutive subjects with normal clinic blood pressure evaluated for sleep disorders. Multivariate linear regression analysis showed that the apnea-hypopnea index (AHI) was an independently associated variable, even after adjustments for age, gender and risk factors for cardiovascular disease, with baPWV (R(2)=0.39, beta=0.19, P<0.01) and the E/A ratio (R(2)=0.51, beta=-0.27, P<0.01). The baPWV and LV relative wall thickness at diastole (RWTd) were significantly higher (P<0.05), and the E/A ratio was significantly lower (P<0.05), in subjects with severe OSA (AHI> or =30 episodes per hour) than in non-OSA subjects (AHI<5 episodes per hour). The analysis also showed that the baPWV bore a significant independent relationship to the RWTd (beta=0.19, P=0.02) and E/A ratio (beta=-0.12, P=0.04) adjusted for the risk factors for cardiovascular disease, the presence of metabolic syndrome and the severity of OSA. Thus, in this study, we showed the existence of increased arterial stiffness of the central to middle-sized arteries and LV structural/functional abnormalities in severe OSA patients, even in subjects with normal clinic blood pressure, suggesting the possible existence of a direct association between OSA and cardiovascular abnormalities.