Sleep apnea and systemic hypertension: a causal association review

Hypertension, or high blood pressure, affects 20 percent of persons and increases the risk of heart disease and circulatory disorders of the brain. However, the mechanism underlying the development of hypertension in many cases is not known. Hypertension has been associated with the sleep apnea syndrome (SAS), a sleep disorder. In SAS, breathing ceases during sleep for at least 10 seconds and this cessation of breathing occurs 30 or more times during the course of sleep. Breathing may cease due to inactivity of the respiratory muscles or blockage of the airways. SAS affects more than one percent of the population. Studies show that circulatory changes occur during apnea and the persistence of such changes may contribute to the development of hypertension and other circulatory disorders. However, more evidence for a role of SAS in causing hypertension is needed to justify the use of costly screening tests for this sleep disorder among hypertensive patients. Hence, the causal relation between SAS and hypertension was assessed by reviewing five epidemiologic studies conducted between 1978 and 1989. The current evidence suggests that SAS is consistently and specifically associated with hypertension. Possible mechanisms underlying the development of both SAS and hypertension are discussed. Although SAS appears to increase the risk of hypertension, the risk relation is not stable and does not justify the need for SAS screening of hypertensive patients. (Consumer Summary produced by Reliance Medical Information, Inc.)