Using the creatinine measures and data on urine albumin, a urine protein that can also signal kidney problems, the researchers diagnosed CKD in 146 of the participants. Rates among African-Americans and whites were similar, with both at about 6 percent.

Prevalence among those with family incomes below the poverty line was 27 percent greater than those living above it. However, when the researchers combined socioeconomic and racial data, they found that low socioeconomic status was associated with a greater prevalence of CKD in African-Americans, but not whites. African-Americans living below the poverty line were 33 percent more likely to have CKD than whites of similar socioeconomic status. The finding persisted even after Crews and her colleagues accounted for other factors known to increase the rate of CKD, including diabetes, high blood pressure, and tobacco, alcohol and drug use.

Crews and her colleagues believe that there are several reasons why socioeconomic status seems to affect the rates of CKD in African-Americans and whites differently, including genetics, stress, and health behaviors such as diet and exercise habits. She notes that the next step will be to tease out the different factors that might contribute to CKD in low-income African Americans.

"We need to figure out why this is happening so that we can develop effective strategies to prevent CKD from developing," Crews says.

Source: Johns Hopkins Medical Institutions