High prevalence of unrecognized sleep apnoea in drug-resistant hypertension

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Abstract
To determine the prevalence of obstructive sleep apnoea (OSA) in adult patients with drug-resistant hypertension, a common problem in a tertiary care facility. Cross-sectional study. University hypertension clinic. Adults with drug-resistant hypertension, defined as a clinic blood pressure of ≥ 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. Prevalence of OSA, defined as an apnoea-hypopnoea index of ≥ 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. 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.