Blood pressure, cardiac structure and severity of obstructive sleep apnea in a sleep clinic population.

OBJECTIVES We investigated whether the severity of obstructive sleep apnea (OSA) predicts blood pressure or cardiac left ventricular thickness in a clinical population of OSA patients, if adjustments are made for age, gender, use of antihypertensive agents, smoking, body mass index, history of coronary artery disease, hypercholesterolemia and circulating C-peptide concentrations. DESIGN Relationships in this cross-sectional study were investigated with correlation analysis and multiple regression procedures. PATIENTS AND METHODS Apnea-hypopnea index (AHI, polysomnography) and office systolic and diastolic blood pressures (SBP and DBP) were measured in 81 subjects referred to a university hospital sleep laboratory. Ambulatory blood pressures were recorded during one 24 h cycle. Left ventricular (LV) muscle size was quantified as two-dimensionally directed M-mode-derived end-diastolic thickness of interventricular septum and posterior chamber wall. RESULTS After adjustment for separate or the entire set of covariates, AHI predicted office SBP and DBP as well as daytime ambulatory DBP and night-time ambulatory SBP and DBP, but not daytime ambulatory SBP. In contrast, associations between AHI and LV muscle thickness reflected complex inter-relationships with confounding variables. Smoking and age suppressed, whereas body mass index (BMI) and hypertension inflated the relationship between OSA severity and LV muscle thickness in this study. CONCLUSIONS AHI is an independent predictor of several measures of blood pressure. OSA severity and LV muscle thickness appear to be primarily linked via increased blood pressure.