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/m(2) 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.