Obstructive Sleep Apnea: The Most Common Secondary Cause of Hypertension Associated With Resistant Hypertension

Recognition and treatment of secondary causes of hypertension among patients with resistant hypertension may help to control blood pressure and reduce cardiovascular risk. However, there are no studies systematically evaluating secondary causes of hypertension according to the Seventh Joint National Committee. Consecutive patients with resistant hypertension were investigated for known causes of hypertension irrespective of symptoms and signs, including aortic coarctation, Cushing syndrome, obstructive sleep apnea, drugs, pheochromocytoma, primary aldosteronism, renal parenchymal disease, renovascular hypertension, and thyroid disorders. Among 125 patients (age52±1 years, 43% males, systolic and diastolic blood pressure176±31 and 107±19 mm Hg, respectively), obstructive sleep apnea (apnea-hypopnea index>15 events per hour) was the most common condition associated with resistant hypertension (64.0%), followed by primary aldosteronism (5.6%), renal artery stenosis (2.4%), renal parenchymal disease (1.6%), oral contraceptives (1.6%), and thyroid disorders (0.8%). In 34.4%, no secondary cause of hypertension was identified (primary hypertension). Two concomitant secondary causes of hypertension were found in 6.4% of patients. Age >50 years (odds ratio5.2 [95% CI1.9–14.2]; P50 years, large neck circumference measurement, and snoring are good predictors of obstructive sleep apnea in this population.