January 21, 2019Cardiology
A recent NIH-funded study showed that about 75% of African-American men and women are likely to develop high blood pressure by age 55, compared to 55% of white men and 40% of white women of the same age.
According to an article published in Circulation (10 December 2018), African-Americans with moderate or severe sleep apnea are twice as likely to have hard-to-control high blood pressure when their sleep apnea goes untreated. The findings, may partially explain why African-Americans suffer hypertension at rates higher than any other group, and can point to screening and treatment of sleep apnea as another important strategy for keeping uncontrolled high blood pressure at bay.
While sleep apnea, a common disorder that blocks the upper airways and causes people to stop breathing during sleep, has been linked to an increased risk of high blood pressure in whites, the association in blacks has been largely understudied. The study followed 664 African-Americans with hypertension who were participants in the Jackson Heart Study, the largest investigation of causes of cardiovascular disease in African-Americans. The authors tested the participants for obstructive sleep apnea (the most common kind) with a special device used overnight in the home. Sleep apnea was then classified as unaffected, mild, moderate, or severe based on the number of times a person either partially or completely stopped breathing during sleep. Results showed that more than a quarter of the participants had moderate or severe sleep apnea and that the condition had gone undiagnosed in almost all of them-i.e., 94% of the cases. The remaining participants had either no sleep apnea, or a milder form of it.
The authors also took blood pressure measurements and found that 48% of the participants had uncontrolled high blood pressure, meaning they had the condition even though they took one or two antihypertensive medications. About 14% had resistant hypertension, meaning they had the condition while on three or more antihypertensive medications. Resistant hypertension is more severe than uncontrolled and carries a higher risk for heart disease and death. The authors then compared measures of sleep apnea to categories of blood pressure control. Results showed that study participants with moderate or severe sleep apnea were twice as likely to have resistant hypertension when compared to participants without sleep apnea. Those with severe sleep apnea were 3.5 times as likely to have resistant hypertension compared to participants without sleep apnea. Somewhat unexpectedly, the authors found no association between milder forms of sleep apnea and uncontrolled or resistant hypertension. The results suggest that African-Americans with more severe forms of sleep apnea are at higher risk of having hard-to-treat hypertension. The current study did not explore what proportion of resistant hypertension is attributable to sleep apnea.
The study did not examine the mechanisms by which sleep apnea increases blood pressure, but the authors noted that earlier studies indicated that untreated sleep apnea can cause blood pressure to surge during sleep and remain high during the day when a patient is awake.