DETERMINANTS OF CIRCADIAN BLOOD-PRESSURE RHYTHM AND BLOOD-PRESSURE VARIABILITY IN OBSTRUCTIVE SLEEP-APNEA

The prevalence of hypertension in patients with obstructive sleep apno ea (OSA) is high and blood pressure profile is characterized by noctur nal blood pressure (BP) elevation and increased nocturnal BP variabili ty. Ambulatory 24-hour-blood pressure monitoring (ABPM) is a valid, no n-invasive method to describe circadian BP variation. Circadian BP pro file and nocturnal BP variability were related to OSA severity (apnoea -hypopnoea index, mean low O-2), age and body mass index (BMI) in 73 p atients with OSA. Prevalence of hypertension was 75%, and in 59% BMI w as greater than 30 kg m(-2). A nocturnal decline of at least 10% from daytime mean BP values (night/day BP ratio <0.9; dipper) was found in only 25% of hypertensive patients and 39% of normotensive patients. Co mparison between dippers and non-dippers showed significant difference s in apnoea severity (apnoea-hypopnoea index 32 + 19 vs. 50 + 23/h, P < 0.01; mean low O-2 84.5 + 4 vs. 80.2 + 5.8%, P < 0.01) but not for a ge and BMI. In multiple regression analyses with age, body mass index, apnoea-hypopnoea index and mean low O-2 as independent and BP ratios and BP variability as dependent variables, sleep apnoea severity was t he only independent predictor for circadian BP rhythm and nocturnal BP variability. The results presented here suggest that independent of a ge and obesity the severity of sleep apnoea is an important determinan t of circadian BP variation and nocturnal BP variability.