Case-control study of 24 hour ambulatory blood pressure in patients with obstructive sleep apnoea and normal matched control subjects

• Published in: Thorax Vol. 55; no. 9; pp. 736 - 740
• Main Authors: Davies, Christopher W H, Crosby, Joy H, Mullins, Rebecca L, Barbour, Charles, Davies, Robert J O, Stradling, John R
• Format: Journal Article
• Language: English
• Published: London BMJ Publishing Group Ltd and British Thoracic Society 01.09.2000; BMJ; BMJ Publishing Group LTD; BMJ Group
• Subjects: Adult; Aged; Aged, 80 and over; Airway management; Alcohol; ambulatory blood pressure; Biological and medical sciences; Blood pressure; Blood Pressure - physiology; Blood Pressure Monitoring, Ambulatory; Cardiovascular system; Case-Control Studies; Diabetes; Family medical history; Humans; Hypertension; Hypertension - etiology; Hypertension - physiopathology; Investigative techniques of hemodynamics; Investigative techniques, diagnostic techniques (general aspects); Male; Medical sciences; Middle Aged; obstructive sleep apnoea; Original; Risk Factors; Sleep Apnea Syndromes - complications; Sleep Apnea Syndromes - physiopathology; United Kingdom > UK; Human; Pathophysiology; Respiratory disease; Sleep disorder; Exploration; Apnea; Lung function; Sleep; Adult; Arterial pressure; Hemodynamics; Ambulatory; Monitoring
• ISSN: 0040-6376; 1468-3296
• DOI: 10.1136/thorax.55.9.736

BACKGROUND There is considerable debate regarding the relationship between obstructive sleep apnoea (OSA) and hypertension. It is unclear whether OSA is an independent vascular risk factor as studies attempting to assess this association have produced conflicting results because of confounding variables such as upper body obesity, alcohol, and smoking. A case-control study of 24 hour ambulatory blood pressure was undertaken in patients with OSA and matched controls to assess whether OSA is an independent correlate of diurnal hypertension. METHODS Forty five patients with moderate to severe OSA and excessive daytime sleepiness were matched with 45 controls without OSA in a sleep study. Matched variables included age, body mass index (BMI), alcohol, cigarette usage, treated hypertension, and ischaemic heart disease. Upper body obesity was compared by waist:hip and waist:height ratios; 24 hour ambulatory blood pressure recordings were performed (before treatment for OSA) in all subjects. RESULTS Patients with OSA had significantly increased mean (SD) diastolic blood pressure (mm Hg) during both daytime (87.4 (10.2) versus 82.8 (9.1); p=0.03, mean difference 4.6 (95% CI 0.7 to 8.6) and night time (78.6 (9.3) versus 71.4 (8.0); p<0.001, mean difference 7.2 (95% CI 3.7 to 10.6)), and higher systolic blood pressure at night (119.4 (20.7) versus 110.2 (13.9); p=0.01, mean difference 9.2 (95% CI 2.3 to 16.1)). The nocturnal reduction in blood pressure (“dipping”) was smaller in patients with OSA than in control subjects. CONCLUSIONS Compared with closely matched control subjects, patients with OSA have increased ambulatory diastolic blood pressure during both day and night, and increased systolic blood pressure at night. The magnitude of these differences is sufficient to carry an increased risk of cardiovascular morbidity. The slight excess of upper body fat deposition in the controls may make these results conservative.