A community-based study of explanatory factors for the excess risk for early renal function decline in blacks vs whites with diabetes: the Atherosclerosis Risk in Communities study.

CONTEXT: The explanation for the excess risk for diabetic renal disease in blacks is uncertain.
OBJECTIVES: To compare the incidence of early renal function decline in black and white adults with diabetes and to examine possible explanatory factors for racial differences.
DESIGN: Prospective cohort study.
SETTING: Four US communities participating in the Atherosclerosis Risk in Communities study. PARTICIPANTS: Community-based sample of 1434 diabetic adults aged 45 to 64 years. MEASUREMENTS: Detailed baseline assessment using structured interview, results of physical examination, and laboratory measurements. MAIN OUTCOME: Development of early renal function decline defined by an increase in serum creatinine of at least 35.4 micromol/L (0.4 mg/dL) during 3 years of follow-up.
RESULTS: During 3 years of follow-up, early renal function decline developed in 45 blacks (28.4 per 1000 person-years [PY]) and 25 whites (9.6 per 1000 PY). After adjustment for age, sex, and baseline serum creatinine level, early renal function decline was more than 3 times as likely to develop in blacks than whites (odds ratio, 3.15; 95% confidence interval, 1.86-5.33). Additional adjustment for education, household income, health insurance, fasting glucose level, mean systolic blood pressure, smoking history, and physical activity level reduced the relative odds in blacks to 1.38 (95% confidence interval, 0.71-2.69), corresponding to a 82% reduction in excess risk.
CONCLUSIONS: These data suggest that early renal function decline is 3 times more likely to develop in blacks than whites and that potentially modifiable factors, including lower socioeconomic status, suboptimal health behaviors, and suboptimal control of glucose level and blood pressure, account for more than 80% of this disparity.