New CARDIA Data: 75% of African-Americans Have Hypertension by Age 55

By age 55, three out of every four African-Americans have already developed hypertension compared with only about half of white individuals, a new study shows.

The new data come from the longitudinal CARDIA study, which has followed black and white adults from four large and diverse areas of the United States for more than 30 years. The elevated risk of hypertension for African-Americans found in the latest analysis is consistent with previous cross-sectional and longitudinal studies, including the National Health and Nutrition Examination Surveys I (NHANES I) Epidemiologic Follow-up Study, which found that the 10-year incidence of hypertension was more than twice as high in black versus white adults.

“It speaks to the fact that we really need to be intervening at a young age,” the study’s lead author, Justin Thomas, PhD (University of Alabama at Birmingham), told TCTMD. “If we wait until people are 40 or 50 to start thinking about hypertension, for the majority of blacks, we've waited too late.”

Published online July 11, 2018, ahead of print, in the Journal of the American Heart Association, the study by Thomas and colleagues defined hypertension according to the stricter treatment recommendations from the 2017 American College of Cardiology (ACC)/American Heart Association (AHA) hypertension guidelines  of less than 130/80 mm Hg, rather than the more relaxed 2014 recommendation from the Eighth Joint National Committee (JNC 8) of less than 140/90 mm Hg. However, African-Americans still had higher BPs than their white counterparts even with the older cutoff, Thomas noted.

“Even using the older definition there was a racial difference by age 30,” he noted. “We're seeing these racial differences at a relatively early age. The new definition simply shifted the percentages a little bit higher, but the differences between the groups did not change.”

Commenting on the study for TCTMD, Keith C. Ferdinand, MD (Tulane Heart and Vascular Institute, New Orleans, LA), said the main message is that "if a person does not have hypertension and they're African-American, their risk of hypertension as they age is going to be quite high, and they should do nonpharmacologic lifestyle measures in order to try to prevent or ameliorate the inexorable increase in blood pressure that you see in this population."

Two Times the Risk

The 3,890 participants in the CARDIA study were enrolled in 1985 and 1986 when they were between the ages of 18 and 30 years. The mean age was 24.7 years, and none had baseline hypertension. Individuals hailed from four regional areas: Birmingham, AL; Chicago, IL; Minneapolis, MN; and Oakland, CA. Approximately every 3 to 5 years, CARDIA participants are followed up for clinical and lifestyle assessments, including fast-food habits, physical activity, smoking status, adherence to a healthy DASH-style diet, and body mass index.

At the 30-year follow up, which forms the basis of the current paper, 75.5% of African-American men and 75.7% of African-American women had hypertension compared with 54.5% of white men and 40% of white women. When the researchers looked at the timing of the development of hypertension they found that by age 46, 50% of African-American men were already hypertensive. In comparison, only 20% and 30%, of white women and white men, respectively, had hypertension by that age. After multivariable adjustment, the risk of developing hypertension was approximately two times higher for black men and women than for white individuals.

The increased risk for hypertension among African-Americans was present at all baseline BP levels, suggesting that “higher BP in childhood does not fully explain racial disparities in hypertension,” according to Thomas and colleagues. To TCTMD, Thomas said at least three studies, including two from the famed Bogalusa Heart Study, have suggested that BP in children as young as 5 years of age is higher for African-Americans than whites.

Early Lifestyle Modification Needed

Lower BMI and adherence to a DASH-style diet were both predictive of lower risk of hypertension regardless of race in the current study, something that both Thomas and Ferdinand said demonstrates the importance of encouraging healthy diets from a very young age.

"These are problems in our society that cannot be minimized and need to be addressed,” Ferdinand said. While the message to embrace a positive lifestyle is challenging to get across to young patients, he noted, "we have some science to justify being more ambitious in attempting lifestyle modification."

Thomas added that something else CARDIA clearly shows is that African-Americans as a whole gain more weight as they age than whites.

“So, it’s likely that what's driving this increase in incidence of hypertension is unhealthy lifestyle in the sense of not eating as well and gaining more weight,” he said. “It’s a tough message because we struggle in all areas of healthcare with young adults because by their very nature they sometimes feel invincible. So, the challenge is in trying to convince them that what they are doing now is going to affect them 15, 20, 30 years down the road.”