High prevalence of unrecognized sleep apnoea in drug-resistant hypertension

OBJECTIVES: To determine the prevalence of obstructive sleep apnoea (OSA) in adult patients with drug-resistant hypertension, a common problem in a tertiary care facility. DESIGN: Cross-sectional study. SETTING: University hypertension clinic. PATIENTS AND METHODS: Adults with drug-resistant hypertension, defined as a clinic blood pressure of > or = 140/90 mmHg, while taking a sensible combination of three or more antihypertensive drugs, titrated to maximally recommended doses. Each of the 41 participants completed an overnight polysomnographic study and all but two had a 24 h ambulatory blood pressure measurement. RESULTS: Prevalence of OSA, defined as an apnoea-hypopnoea index of > or = 10 obstructive events per hour of sleep, was 83% in the 24 men and 17 women studied. Patients were generally late middle-aged (57.2 +/- 1.6 years, mean +/- SE), predominantly white (85%), obese (body mass index, 34.0 +/- 0.9 kg/m2) and taking a mean of 3.6 +/- 0.1 different antihypertensive medications daily. OSA was more prevalent in men than in women (96 versus 65%, P = 0.014) and more severe (mean apnoea-hypopnoea index of 32.2 +/- 4.5 versus 14.0 +/- 3.1 events/h, P = 0.004). There was no gender difference in body mass index or age. Women with OSA were significantly older and had a higher systolic blood pressure, lower diastolic blood pressure, wider pulse pressure and slower heart rate than women without OSA. CONCLUSIONS: The extraordinarily high prevalence of OSA in these patients supports its potential role in the pathogenesis of drug-resistant hypertension, and justifies the undertaking of a randomized controlled trial to corroborate this hypothesis.