Sleep-related breathing disorder is an independent risk factor for uncontrolled hypertension

Objective To test the hypothesis that sleep-related breathing disorder (SRB D) is associated with poor blood pressure control in hypertensive patients independent from confounding factors such as age, body mass index, alcohol, smoking and daytime blood gases. Design and methods This cross-sectional study of a sleep laboratory cohort was carried out at the University Hospital Sleep Disorders Centre, Marburg. The study comprised 599 patients referred for a sleep study, all of them w ith a documented history of systemic hypertension and/or previously initiat ed antihypertensive therapy. Data were obtained from a clinical interview, two unattended sleep studies and assessment of clinic blood pressure, chole sterol level, alcohol and nicotine consumption and daytime blood gases. The main outcome measure was a post hoc analysis of predictors for poor blood pressure control. Results Respiratory disturbance index (RDI) was significantly higher in pat ients with uncontrolled hypertension (blood pressure greater than or equal to 160 and/or 95 mmHg, n = 463) than in those with controlled hypertension (n = 136) (34.0 +/- 26.8 versus 27.0 +/- 23.5, P < 0.01). The relative prop ortion of patients with uncontrolled hypertension increased significantly a s SRBD activity increased (chi(2), p < 0.05). Body mass index was the only independent predictor (P = 0.006) of uncontrolled hypertension in the whole study sample. However, in the subset of patients aged less than or equal t o 50 years, RDI (P = 0.006) and age (P = 0.016) were the only independent p redictors. The probability of uncontrolled hypertension increased by approx imately 2% (B = 0.019, P = 0.006) for each RDI unit. Conclusion SRBD should be considered, in addition to traditional confounder s, as a risk factor for poor blood pressure control in younger hypertensive patients (less than or equal to 50 years of age). J Hypertens 2000, 18:679 -685 (C) Lippincott Williams & Wilkins.