Why do blacks with advanced kidney disease live longer than whites?

Blacks in the United States are more likely to require dialysis and develop end stage renal disease (ESRD) than whites, but they also live longer than whites once they reach later stages of kidney disease. A study of this phenomenon will appear in an upcoming issue of the Clinical Journal of the American Society Nephrology (CJASN). Csaba P. Kovesdy, MD (Salem VA Medical Center), John E. Anderson, MD, Stephen F. Derose, MD, and Kamyar Kalantar-Zadeh, MD, PhD (University of California Los Angeles), investigated by comparing 298 black and 945 white male patients with moderate and advanced chronic kidney disease (CKD) who were not on dialysis and who were treated within the Veteran Health Administration (VA) System.

"Studying patients with non-dialysis dependent CKD is important to determine the reasons behind the higher incidence of ESRD in blacks in order to address the root causes of this discrepancy," said Dr. Kovesdy. Conducting the study within the VA System allowed the researchers to analyze a group of patients in which blacks and whites had similar access to health care.

The investigators found that the rates of kidney function decline were similar in blacks and whites, but blacks were less likely to die once they reached moderate to advanced kidney disease. The lower death rates in black patients with later stages of disease were mainly due to a lower prevalence of cardiovascular disease; the higher incidence of ESRD was explained by clinical characteristics such as lower initial kidney function.

The authors' suspect that lower death rates among blacks with moderate to advanced kidney disease is due to higher death rates among blacks in earlier stages of kidney disease. Blacks who survive earlier stages have fewer health issues (such as cardiovascular disease) than whites. This would explain why blacks had better survival rates than whites among the VA patients. "These survival discrepancies are quite different from what is seen in the general population, where black Americans typically experience higher mortality and lower life expectancy than whites," said Dr. Kovesdy. "More research is needed to explain these differences and to alleviate the racial and ethnic discrepancies in health outcomes in the US," he added.

Source: American Society of Nephrology