Albumin marker flags incident CHD risk in blacks

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Blacks with albuminuria appear to be at higher risk of incident coronary heart disease (CHD) than whites, according to a study published Aug. 21 in JAMA. But risk was similar for both races for recurrent CHD.

In a previous study, the Reasons for Geographic and Racial Differences in Stroke (REGARDS) research team explored the racial differences between excess urinary albumin excretion and incident stroke. They found an association for albumin-to-creatinine ratio (ACR) of 30 mg/g or more and greater risk of incident stroke in blacks but not whites.

Led by Orlando M. Gutierrez, MD, of the University of Alabama at Birmingham, the REGARDS researchers looked at the association of urinary ACR and CHD. They reasoned that since ACR is a risk factor for cardiovascular disease, racial differences in ACR might contribute to disparities in CHD.

REGARDS had enrolled more than 30,000 adults, age 45 years and older, between January 2003 and October 2007, and included baseline urinary ACR among its clinical data. For this analysis, Gutierrez et al identified 23,273 participants without CHD and 4,934 with CHD and stratified ACR into four categories ranging from less than 10 mg/g to more than 300 mg/g.

At a median 4.5 years follow-up, there were 616 incident CHD events. In both blacks and whites, higher ACR was associated with a higher risk of incident CHD.

The incidence rates for the two highest categories—30 to 300 mg/g and more than 300 mg/g— were higher in black participants compared with whites (11.2 vs. 8.4 percent and 20.6 vs. 13.6 percent, respectively). In adjusted analyses, blacks in the highest ACR category had a three-fold increased risk of incident CHD compared with blacks in the lowest category, while there was no statistically significant difference between whites in the lowest and highest categories.

Looking at recurrent CHD, they found higher ACR was associated with a greater risk of recurrent CHD for both races, even after adjustments.

“Although the absolute risk differences in the two highest categories of ACR were relatively small (approximately equal to four and seven extra events per 1,000 person-years of follow-up in black vs white participants, respectively), given the link between elevated urinary ACR and systemic microvascular injury, these data suggest that black individuals have greater susceptibility to vascular disease than white individuals, which, in turn, may account for much of their excess risk of cardiovascular disease events such as stroke and CHD,” they wrote.

ACR is a marker of kidney disease. Kidney disease may place blacks at higher risk of CHD, they proposed, as could the faster progression to late-stage kidney disease seen in blacks.

They described the reasons for the recurrent CHD findings as “unclear.” Blacks may be less likely than whites to receive preventive care for CHD, Gutierrez et al offered, but once they experience a CHD event their secondary care might be equivalent with whites.

In an accompanying editorial, Daniel E. Weiner, MD, of Tufts Medical Center in Boston, and Wolfgang C. Winkelmayer, MD, ScD, of Stanford University School of Medicine in Palo Alto, Calif., raised the questions of why ACR is higher in blacks and how CHD risk can be reduced. They wrote that equal access to healthcare resources and providing healthy living strategies early in life are needed to tease out genetic factors from other factors.

The latest REGARD findings shed light on the association between ACR and CHD, and may be useful for CHD risk stratification, particularly in blacks, they concluded.