One Third of CVD in US Blacks Linked to Hypertension

October 23, 2019

One third of cardiovascular disease cases in the US black population are associated with hypertension, new research shows.

"Our data support focused efforts to diagnose and treating hypertension in black individuals, and even more importantly, attempting to prevent the development of hypertension in the first place with lifestyle modifications," said lead author, Donald Clark III, MD, University of Mississippi Medical Center, Jackson.

The study was published online in JAMA Cardiology on October 23.

The authors set out to establish the population-attributable risk for cardiovascular disease associated with hypertension in black individuals. They explain that population-attributable risk represents the proportion of cases of a disease in a population that can be attributed to a specific risk factor. It accounts for both the prevalence of a risk factor and the excess risk for disease associated with that risk factor.

"The population-attributable risk can be used to inform policy and prioritize public health interventions by identifying modifiable risk factors that can have the greatest association with reducing disease risk," they note.

"The population-attributable risk takes into account prevalence as well as hazard so allows us to comprehensively assess the effect of hypertension on a population level," Clark told Medscape Medical News.

Results of the cohort study of 12,497 black participants in the United States showed a population-attributable risk for cardiovascular disease associated with hypertension of 32.5%.

"That means that among all cases of cardiovascular disease — including CV death, MI, stroke and heart failure — 1 in 3 of these events can be attributed to hypertension, and if we eliminated hypertension at a population level we could reduce CV events by 33%," Clark said.

Based on the known high prevalence of hypertension in the black population, Clark notes that this was not an entirely surprising finding. But it has significant public health relevance, and reinforces that reducing hypertension over the life course should significantly reduce CV disease in this population," he said. "This sort of data is important to prioritize basic health interventions."

The authors conclude that this study "adds to previous work showing that hypertension was associated with a larger proportion of cardiovascular events compared with other traditional risk factors, including diabetes, hypercholesterolemia, obesity, and smoking."

When stratifying the data by age and CV outcomes, the researchers found that there was an especially large impact of hypertension on stroke and this was larger in younger people. "The population-attributable risk for stroke in black individuals under 60 years of age was almost 70%, so lowering blood pressure in younger black individuals will bring about a particularly large benefit in terms of a reduction in future stroke," Clark commented.

"Younger adults are thought to be at lower cardiovascular risk, but their lifetime risks are actually higher," he pointed out.

Noting that both racial and geographic disparities in healthcare exist that result in the black population receiving less care, Clark said their data confirm that "reducing hypertension in black individuals should be a major public health priority."

"There needs to be broader public health discussions about ways to improve diagnosis and treatment of hypertension in the black population as well as prevention initiatives such as lowering the amount of salt in the food supply," he added.

While similar studies have been done before, this latest research is based on much larger cohorts than have been considered before and that more broadly represent the US population, he said.

For the current study, the researchers used data on 12,497 black participants without cardiovascular disease at baseline. They included those enrolled in the Jackson Heart Study (JHS) from 2000 to 2004 and followed for cardiovascular events up to 2015, or those enrolled in the REasons for Geographic and Racial Differences in Stroke (REGARDS) study from 2003 to 2007 and followed for cardiovascular events until 2016.

Normal blood pressure and hypertension were defined using the 2017 American College of Cardiology/American Heart Association blood pressure guideline thresholds.

The prevalence of hypertension among non-Hispanic black US adults without cardiovascular disease was calculated using data from the National Health and Nutrition Examination Survey (NHANES) 2011-2014.

Results showed that of the participants in the JHS and REGARDS studies, 1935 had normal blood pressure, 929 had elevated blood pressure, and 9633 had hypertension. For a maximum 14.3 years of follow-up, 9.9% of study participants experienced a cardiovascular disease event.

The multivariable-adjusted hazard ratio associated with hypertension was 1.91 for cardiovascular disease, 2.41 for coronary heart disease, 1.52 for heart failure, and 2.20 for stroke.

The prevalence of hypertension was 53.2% among non-Hispanic black individuals. The population-attributable risk associated with hypertension was 32.5% for cardiovascular disease, 42.7% for coronary heart disease, 21.6% for heart failure, and 38.9% for stroke.

The population-attributable risk for cardiovascular disease associated with hypertension was higher among those younger than 60 years (54.6%) compared with those 60 years or older (32.0%).

Among adults receiving antihypertensive medication, the population-attributable risk was smaller among participants with lower blood pressure levels, emphasizing the importance of effective hypertension management, the researchers write.

Furthermore, within each blood pressure level studied, the population-attributable risk was higher among participants receiving versus not receiving antihypertensive medication. These findings highlight the excess cardiovascular disease risk among adults with hypertension as not entirely mitigated by pharmacologic therapy, they note.

"To achieve maximum population health benefit, the present results suggest that effective interventions are needed for primordial prevention of elevated blood pressure," the authors state.

"Various nonpharmacologic interventions, including regular physical activity, weight control, adopting a heart healthy diet such as the Dietary Approaches to Stop Hypertension eating plan, and minimizing alcohol intake, have been shown to help prevent the development of hypertension," they add.

The REGARDS study was supported by grants from the National Institutes of Health and the American Heart Association. The Jackson Heart Study was supported and conducted in collaboration with Jackson State University, Tougaloo College, the Mississippi State Department of Health, and the University of Mississippi Medical Center, and contracts from the National Heart, Lung, and Blood Institute and the National Institute on Minority Health and Health Disparities. Clark has disclosed no relevant financial relationships.

JAMA Cardiol. Published online October 23, 2019. Abstract.

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