Racial differences in kidney function among individuals with obesity and metabolic syndrome: results from the Kidney Early Evaluation Program (KEEP).

Background: Obesity and metabolic syndrome may differ by race. For participants in the National Kidney Foundation's Kidney Early Evaluation Program (KEEP), we examined whether African American and white participants with obesity and metabolic syndrome differ regarding albuminuria, estimated glomerular filtration rate (eGFR), anemia, and bone/mineral metabolism derangements in chronic kidney disease (CKD).

Methods: 3 study cohorts were assembled: (1) eligible African American and white KEEP participants with body mass index > or = 30 kg/m(2), (2) a subgroup meeting criteria for metabolic syndrome, and (3) a subgroup with eGFR < 60 mL/min/1.73 m(2) and laboratory measurements for hemoglobin, parathyroid hormone, calcium, and phosphorus. Patient characteristics and kidney function assessments were compared and tested using chi(2) (categorical variables) and t test (continuous variables). Univariate and multivariate logistic regression analyses were performed to evaluate associations of race with kidney disease measures.

Results: Of 37,107 obese participants, 48% were African American and 52% were white. Whites were more likely to have metabolic syndrome components (hypertension, 87.1% vs 84.8%; dyslipidemia, 81.6% vs 66.7%; diabetes, 42.7% vs 34.9%) and more profoundly decreased eGFR than African Americans (CKD stages 3-5 prevalence, 23.6% vs 13.0%; P < 0.001). African Americans were more likely to have abnormal urinary albumin excretion (microalbuminuria, 12.5% vs 10.2%; OR, 1.60 [95% CI, 1.45-1.76]; macroalbuminuria, 1.3% vs 1.2%; OR, 1.61 [95% CI, 1.23-2.12]) and CKD stages 1-2 (10.3% vs 7.1%; OR, 1.54 [95% CI, 1.38-1.72]). For participants with CKD stages 3-5, anemia prevalence was 32.4% in African Americans and 14.1% in whites; corresponding values for secondary hyperparathyroidism were 66.2% and 46.6%, respectively.

Conclusions: Obesity and metabolic syndrome may be heterogeneous disease states in African Americans and whites, possibly explaining differences in long-term kidney and cardiovascular outcomes.