Metabolic syndrome, proteinuria, and the risk of progressive CKD in hypertensive African Americans

Background: Chronic kidney disease (CKD) is more likely to progress to kidney failure (end-stage renal disease) in African Americans, although the reasons for this are unclear. Metabolic syndrome is a risk factor for the development of diabetes and cardiovascular disease and recently was linked to incident CKD. The purpose of this study is to examine whether metabolic syndrome is associated with kidney disease progression in hypertensive African Americans. Design & Participants: The current study design is a secondary analysis of the African-American Study of Hypertension and Kidney Disease, a randomized controlled trial of blood pressure goal and agents in hypertensive African Americans with CKD. Predictors: Metabolic syndrome was defined according to the modified National Cholesterol Education Program guidelines. Outcomes: Decrease in glomerular filtration rate of 50% or 25 mL/min/1.73 m(2), end-stage renal disease (initiation of dialysis therapy or transplantation), death, or a composite outcome of all 3. Results: 842 subjects were included in this analysis, and 41.7% met criteria for metabolic syndrome. Subjects meeting criteria for metabolic syndrome had greater levels of proteinuria. Cox regression analyses adjusted for age, sex, glomerular filtration rate, and other significant covariates except for proteinuria indicated a 31% increased risk, with a 95% confidence interval of 1.03 to 1.7(P = 0.03) for time to reach the composite outcome in those with metabolic syndrome. Adjusting for proteinuria, the effect was abated to 16% (95% confidence interval, 0.9 to 1.5), no longer remained significant (P = 0.2), and was unchanged by adjusting randomized treatment group (blood pressure goal or antihypertensive drug). Limitations: Lack of waist circumference as a better surrogate of abdominal obesity. Conclusions: In summary, metabolic syndrome is associated with proteinuria in hypertensive African Americans, but is not independently associated with CKD progression.