Systolic BP in Young Black Adults Linked to Later Risk of CVD

In young adult black individuals, systolic blood pressure (SBP), but not diastolic blood pressure (DBP), is associated with development of cardiovascular disease by the age of 58, according to a new study[1].

“In general, we’ve felt that, for everyone, diastolic hypertension in young people tends to be a problem that confers risk. And only beyond age 50 do we really start to worry about systolic hypertension conferring risk,” senior author Dr. Donald M Lloyd-Jones (Northwestern University Feinberg School of Medicine, Chicago) told heartwire from Medscape.

“What our data suggest is that the older paradigm has been based on largely white populations. In younger groups there may be a difference between African Americans and whites, suggesting that even in younger African Americans systolic blood pressure is the component that seems to be conferring risk for early-onset cardiovascular disease, whereas in whites the longstanding paradigm did seem to be true,” he added.

The analysis, published online February 15, 2017 in JAMA Cardiology, involved 4880 participants (45.6% male; 50.7% black) enrolled the Coronary Artery Risk Development in Young Adults (CARDIA) study between January 1985 and December 1986. Participants underwent serial examinations seven times to year 25 after baseline assessment, and for examinations between baseline and year 15, research staff took brachial artery blood-pressure measurements three times at 1-minute intervals. Nearly all (94%) survivors had at least one telephone interview or examination between August 2009 and August 2014. CVD events were recorded through September 2013.

At baseline, the mean patient age was 24.9 years, and mean baseline blood pressure was 112/69 mm Hg in blacks and 109/68 mm Hg in whites. Significantly more blacks than whites had hypertension (5.4% vs. 2.8%), defined as an SBP of >140 mm Hg, a DBP of >90 mm Hg, or use of antihypertensive medication; and more blacks were taking antihypertensives (3.2% vs 1.4%).

During a median follow-up of 24.5 years, 140 CVD events occurred among black individuals (2.85 per 1000 person-years; 95% CI 2.41–3.36), compared with 70 events among white individuals (1.37 per 1000 person-years; 95% CI 1.09–1.73).

When systolic and diastolic BP were considered jointly in adjusted analyses, baseline systolic BP (hazard ratio [HR] per 1-SD increase 1.32, 95% CI 1.09–1.61) but not DBP (HR 1.05, 95% CI 0.88–1.26) was significantly associated with CVD risk in young blacks, while diastolic BP (HR 1.74, 95% CI 1.21–2.50) was associated with CVD risk in young whites, but not SBP (HR 0.82, 95% CI 0.57–1.18).

In quartile analyses, the researchers found that in the highest quartile of SBP (≥119 mm Hg), CVD risk was significant among blacks but not whites; whereas in the highest quartile of DBP (≥75 mm Hg), CVD risk was significant in whites but not blacks.

In middle age (mean age 40 years), SBP better identified incident CVD than DBP in both blacks (HR 1.64, 95% CI 1.25–2.16) and whites (HR 1.67, 95% CI 1.02–2.69).

“The cumulative damage of elevated blood pressure, even within what we would call normal or prehypertensive range, seems to be somewhat irreversible and what’s putting people at risk for heart disease and stroke much earlier in life than should otherwise be the case,” Lloyd-Jones told heartwire.

Dr Ann Marie Navar (Duke Clinical Research Institute, Durham, NC), who coauthored an accompanying invited commentary[2], told heartwire , “This study highlights a couple of really important things. The first is that black adults had twice the rate of heart disease as white adults. Most of the heart disease is premature cardiovascular disease. There’s still a big disparity in the burden of cardiovascular disease in white and black adults in the US.

“An important finding of the study is that most adults in the study did not have what we would consider hypertensive levels of blood pressure. Even at what we currently consider blood pressures below thresholds for treatment, having elevated blood pressure early in life over the long run increased people’s risk of heart disease,” she said.

“We need to be thinking about risk factors for heart disease in the same way that we think about pack-years for smoking,” she continued. “Risk factors for heart disease over time accumulate, and there are a number of studies that show even small elevations in risk factors like cholesterol and blood pressure over time cause substantial cumulative risk.

“What that means for clinicians is seeing small elevations in blood pressure or small elevations in cholesterol early in life over time can cause significant cardiovascular disease risk, and we need to be more aggressive in talking to our patients about the cumulative impact of sustained exposure to risk factors and working on prevention of development of hypertension in the first place,” she concluded.

In the invited commentary, Navar and Dr Eric Peterson (Duke Clinical Research Institute) write that studies such as the current one show that there is still much to learn about hypertension.

They concluded, “Several things are clear. First, hypertension is not likely to be one disease. Second, the risk for elevated [systolic blood pressure] and [diastolic blood pressure] appear to be altered by race and age. Third, even low levels of elevated BP appear associated with future harm. As we move forward, the future of personalized medicine will require deeper understanding of the physiology behind hypertension, with the ultimate goal of individualized prognostic and treatment approaches.”

Original Media Source: Heartwire from Medscape