November 24, 2010 (Denver, Colorado) — African Americans and some Hispanic people have significantly faster rates of decline in kidney function prior to the onset of chronic kidney disease (CKD), according to research presented here at Renal Week 2010: American Society of Nephrology 43rd Annual Meeting.
Researchers evaluating data on 5179 patients in the Multi-Ethnic Study of Atherosclerosis (MESA), a nationwide study of heart disease risk factors, found that kidney function in African Americans declined at a rate that was approximately 60% faster than white participants over a 5-year period.
Rates of decline were also significantly higher for certain subgroups of Hispanics.
The racial differences were not explained by traditional risk factors, such as smoking, diabetes, cholesterol, or high blood pressure.
"We adjusted for the traditional risk factors that affect kidney function and it didn't change things very much," said the study's lead author, Carmen J. Peralta, MD, from the University of California at San Francisco and the San Francisco Veteran's Affairs Medical Center.
Subjects in the study had normal kidney function at baseline. Rates of kidney function decline were estimated according to change in the estimated glomerular filtration rate (eGFR) of cystatin C and creatinine.
Baseline levels of creatinine eGFR were greater than 60 mL/min per 1.73 m2, and mean decreases in cystatin C and creatinine eGFR were 1.1 and 1.5 mL/min per 1.73 m2 per year, respectively.
Rates of cystatin C eGFR decline were higher in blacks than whites (1.4 vs 0.88 mL/min per 1.73 m2 per year), and the difference was not attenuated by adjustment for age, sex, income, education, levels of high-density-lipoprotein or low-density-lipoprotein cholesterol, body mass index, C-reactive protein level, smoking, diabetes, hypertension, or systolic blood pressure.
Rates of decline in kidney function among Hispanics, compared with whites, were only statistically significant for Dominicans, who had the fastest rate of decline compared with whites (β, 0.55; P <.011), followed by Puerto Ricans (β, 0.47; P = .03), after full adjustment; Mexicans, South Americans, and other Hispanics did not differ significantly from whites.
African Americans are known to have a faster rate of decline from CKD to end-stage renal disease; however, Dr. Peralta said that her study is the first to take a closer look at the earliest stages of kidney decline.
"This is the first study to evaluate [the rate of decline] using repeated periods of time with 2 markers of kidney function," she said. "If we can find differences early, it opens opportunities for prevention and savings."
The findings are highly significant in terms of suggesting an earlier starting point for intervention to slow or prevent the progression of kidney decline in a population known to have a higher risk.
"This tells us we can detect differences by race very early, which is important for public health, particularly because we know this issue costs as much as $24 billion a year in Medicare costs," Dr. Peralta explained.
"Early decline prior to chronic kidney disease has not been a primary focus of the problem, but I think it should be a part of our future," she said. "There has been a lot of discussion about who is at high risk, but we need to carry that forward and perhaps identify risk factors and consider early intervention."
The findings underscore the need to pay closer attention to warning signs in populations that are at a higher risk for kidney disease, said Thomas H. Hostetter, MD, professor of medicine and director of the nephrology division at the Albert Einstein College of Medicine in New York City.
"The findings are not really surprising, but it's good to see the data well analyzed," he said.
"I think more vigilance in high-risk populations is warranted, but the tools are weak at present. However, family history, blood pressure, and probably urinary protein/albumin would be reasonable as indications for closer follow-up of patients when GFR estimates are near normal in high-risk racial groups."
Dr. Peralta and Dr. Hostetter have disclosed no relevant financial relationships. Two other authors on the study, Ian H. de Boer, MD, and Bryan Kestenbaum, MD, report receiving grants or research support from Abbott Laboratories and Amgen, respectively.
Renal Week 2010: American Society of Nephrology 43rd Annual Meeting: Abstract FC090. Presented November 18, 2010.
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