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Nearly Half of African Americans Have Masked Hypertension

Data presented this week confirm the high prevalence of masked hypertension in African Americans, with investigators reporting that masked hypertension is prevalent in 45% of African Americans during any single office visit….

The results suggest that blood-pressure monitoring in the office might not be sufficient to assess cardiovascular-risk exposure in this population and that out-of-office blood pressure monitoring might be needed to expose underlying hypertension.

“Masked hypertension is known to be a precursor of sustained hypertension,” according to lead investigator Dr. Praveen Veerabhadrappa (Temple University, Philadelphia, PA). “In a large study conducted in 2010, it was observed that 48% of individuals with masked hypertension went on to develop sustained hypertension for a period of 10 years. Second, we know that the risk factors associated with masked hypertension are equal to that of sustained hypertensives and are worse compared with normotensives.”

Veerabhadrappa said the prevalence of masked hypertension is known to be as high as 70% in African Americans, a rate that is significantly higher than the approximate 10% reported in the general population. These findings, however, were typically based on a single office visit, and it is unknown whether this high prevalence is the result of a systematic change in blood pressure or the result of an outlier measurement.

In this study, the researchers measured blood pressures of 32 African Americans considered generally healthy. Despite a body-mass index of 30 kg/m2, the individuals did not smoke, were free from diabetes and cardiovascular disease, and were not currently taking antihypertensive medications. During their analysis, blood pressure was recorded over three visits, with the average blood pressure taken from three different measurements. Masked hypertension was defined as a daytime blood pressure >130/85 mm Hg and nighttime >120/70 mm Hg.

Mean Office and Ambulatory Blood Pressures: 

Blood-pressure measurement occurrence
Systolic blood pressure (mm Hg)
Diastolic blood pressure (mm Hg)
First office visit
124.4
79.1
Second office visit
126.4
80.1
Third office visit
128.7
79.1
24-hour
126.7
78.4
Daytime
128.4
80.2
Nighttime
116.8
68.6
 

Overall, 59% of individuals were identified as having masked hypertension based on blood pressure obtained during the first office visit. By visits two and three, the prevalence of masked hypertension was 40% and 38%, respectively. The average prevalence of masked hypertension was 45% in this African American population.

Office blood pressure systematically fails to identify masked hypertension,” said Veerabhadrappa. “Office blood-pressure measurements might not be sufficient, especially in this cohort.”

Dr. Robert Phillips (University of Massachusetts Medical School, Worcester), commenting on the results of the study, said that the end-organ damage, even with equivalent levels of blood pressure, within the African American community is significantly greater that other populations, with African Americans having significantly higher rates of stroke, kidney disease, and heart failure. Phillips said that blood pressures of African Americans might be measured as artificially normal, when in fact they are exposed to the end-stage risks caused by hypertension.

“The implication then is that we can’t be complacent with a normal blood pressure in an African American [measured] inside the office,” said Phillips. “We’re going to have to do more ambulatory and home blood-pressure monitoring.”

Presented at the American Society of Hypertension (ASH) 2011 Scientific Meeting