Is obstructive sleep apnea a common cause of essential hypertension?

Obstructive sleep apnea (OSA) occurs in about 10% of the middle-aged population but in about 30% of the hypertensive population of the same age. About 20% of the middle-aged population has hypertension but about 50% of patients with OSA have hypertension. Despite this close relationship between these two entities, previous attempts to determine whether the respiratory abnormalities in OSA were responsible for the hypertension were inconclusive, particularly because of the confounding effect of obesity which is common to both conditions. Data from recent observational and intervention studies, however, have succeeded in avoiding many of the pitfalls of earlier studies and it is now becoming evident that OSA may be a major cause of hypertension--responsible for about 30% of all cases. Successful treatment of OSA by any means has been shown in most studies to cause significant reductions in blood pressure throughout the 24 h period, while at the same time alleviating the vast array of symptoms and clinical abnormalities associated with this common and serious condition. Despite the encouraging results of these recent data, more studies are urgently required which should include larger numbers of patients and controls in order to clarify further the relationship between OSA and hypertension.