Proteinuria Is Indicator of Heart Disease Risk in Whites, Not Blacks

The cardiovascular risk that is associated with proteinuria, or high levels of protein in the urine, a common test used by doctors as an indicator of increased risk for progressive kidney disease, heart attack, and stroke, has race-dependent effects, according to a new study by researchers at Wake Forest University School of Medicine. The study appears in Diabetes Care.

“Proteinuria, a long accepted indicator of heart disease risk, has far less impact on blacks than it does on whites,” says Barry Freedman, MD, John H. Felts III Professor, chief of the section on nephrology, and lead study researcher. “In the medical community, it is believed that the more protein in a patient’s urine, the greater the risk for heart disease and stroke, and this is true—in white populations."

In the general community, blacks have more heart disease risk factors than whites, including higher blood pressures and LDL cholesterol levels, and higher blood sugars in patients with diabetes, Freedman explains. As such, they face a higher risk for heart attack than whites, he says.

However, several large studies have shown that despite having more risk factors for hardening of the arteries, black men had less calcium in the heart arteries compared with white men. In addition, given access to equivalent healthcare as whites, blacks with diabetes face only one half the risk of a heart attack, indicating that blacks appear to somehow be protected from the cardiovascular effects of these risk factors, Freedman says.

The level of urine protein was examined in 835 white participants and 393 black participants, all with diabetes. Participants were also tested for atherosclerosis, based on the buildup of calcium in their major arteries.

The research team found that in the white population, greater amounts of protein in the urine were directly associated with higher levels of atherosclerosis. This association, however, was not seen in the black study population.

“It turns out that urinary protein, an accepted predictor of calcium buildup and risk factor for heart attack that we have long relied upon, is a much stronger indicator in whites than blacks,” Freedman says. This finding is important, Freedman adds, because blacks with diabetes and kidney failure tend to live significantly longer after starting kidney replacement therapy (dialysis) and suffer fewer heart attacks, compared with whites.

Source: Wake Forest University Baptist Medical Center