Relationship Between Body Mass Index and Proteinuria in Hypertensive Nephrosclerosis: Results From the African American Study of Kidney Disease and Hypertension (AASK) Cohort

Background: Few studies have examined the association between obesity and markers of kidney injury in a chronic kidney disease population. We hypothesized that obesity is independently associated with proteinuria, a marker of chronic kidney disease progression. Study Design: Observational cross-sectional analysis. Setting & Participants: Post hoc analysis of baseline data for 652 participants in the African American Study of Kidney Disease (AASK). Predictors: Obesity, determined using body mass index (BMI). Measurements & Outcomes: Urine total protein-creatinine ratio and albumin-creatinine ratio measured in 24-hour urine collections. Results: AASK participants had a mean age of 60.2 +/- 10.2 years and serum creatinine level of 2.3 +/- 1.5 mg/dL; 61.3% were men. Mean BMI was 31.4 +/- 7.0 kg/m(2). Approximately 70% of participants had a daily urine total protein excretion rate <300 mg/d. In linear regression analyses adjusted for sex, each 2-kg/m(2) increase in BMI was associated with a 6.7% (95% CI, 3.2-10.4) and 9.4% (95% CI, 4.9-14.1) increase in urine total protein-creatinine and urine albumin-creatinine ratios, respectively. In multivariable models adjusting for age, sex, systolic blood pressure, serum glucose level, uric acid level, and creatinine level, each 2-kg/m2 increase in BMI was associated with a 3.5% (95% CI, 0.4-6.7) and 5.6% (95% CI, 1.5-9.9) increase in proteinuria and albuminuria, respectively. The interaction between older age and BMI was statistically significant, indicating that this relationship was driven by younger AASK participants. Limitations: May not generalize to other populations; cross-sectional analysis precludes statements regarding causality. Conclusions: BMI is associated independently with urine total protein and albumin excretion in African Americans with hypertensive nephrosclerosis, particularly in younger patients. Am J Kidney Dis 56: 896-906. (C) 2010 by the National Kidney Foundation, Inc.