Kidney Disease Research Updates
Spring/Summer 2009

Study Helps Explain Greater Percentage of African Americans on Dialysis

Scientists are unsure why a relatively greater number of African Americans compared with Caucasians suffer from kidney failure, also called end-stage renal disease (ESRD). One possible reason for this phenomenon, some scientists believe, is that advanced chronic kidney disease (CKD) may progress faster in African Americans. A recent study funded by the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), however, sheds doubt on this hypothesis.

“The higher crude ESRD rate in African Americans appears to result from lower mortality in the late stages of CKD, not faster progression of CKD,” Csaba P. Kovesdy, M.D., chief of Nephrology, Salem Veteran’s Administration Medical Center, Salem, VA, and co-authors wrote in a report that appeared April 15 in the Clinical Journal of the American Society of Nephrology. Other possible explanations for the greater incidence of ESRD among African Americans include greater prevalence of CKD, faster decline in kidney function in early CKD, fewer kidney transplantations, or some combination thereof.

A Growing Problem

CKD, most often a complication of hypertension and diabetes, is becoming increasingly prevalent in the United States, especially among certain minorities—including African Americans. Many of the estimated 23 million Americans with CKD are unaware they have kidney disease. The kidney damage caused by CKD is usually irreversible; however, treatment can slow its progression to ESRD. Dialysis and kidney transplantation are the only two available treatments for ESRD.

The current study aimed to compare survival and rate of kidney function decline between African American and Caucasian men with moderate to advanced CKD who were referred for evaluation by a kidney specialist. The study included 298 African American men and 945 Caucasian men. At the baseline visit, none had started dialysis. After examining participants and taking health histories, the researchers monitored body mass index, blood pressure, and kidney function for an average of 3 years. Primary outcomes measured were death or initiation of dialysis.

Outcomes

During the study, 267 participants started dialysis and 451 patients died without having started dialysis. Although relatively more African Americans survived and more started dialysis, the researchers accounted for these differences based on factors such as younger age and less cardiovascular disease among the African Americans. The rate of kidney function decline was greater among African Americans, but it, too, was not statistically significant.

“We found a significantly higher incidence of ESRD in African American patients, but we could not substantiate the hypothesis that a faster progression of CKD is the reason for the higher incidence of ESRD in African Americans,” wrote Kovesdy and colleagues.

When comparing outcomes based on race and the presence or absence of cardiovascular disease, African Americans without cardiovascular disease had the lowest mortality, but a smaller subset of African Americans with cardiovascular disease had the highest mortality. Data from other studies suggest African Americans in the general population and those with mild to moderate CKD have a higher mortality rate. The authors speculate that “higher mortality of African American patients in the earlier stages of the CKD may result in the selection of a subgroup with fewer comorbidities and better survival in later stages of CKD.”

For more information about CKD, including easy-to-read booklets and fact sheets, visit the National Kidney and Urologic Diseases Information Clearinghouse at www.kidney.niddk.nih.gov.

NIH Publication No. 09–4531
August 2009

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