Obesity modulates the association between systolic blood pressure and albuminuria

Abstract

Background. Obesity is associated with albuminuria and incident kidney disease. Increased vulnerability of the glomerular microcirculation to elevated systemic blood pressure is postulated to contribute to adverse effects of obesity on the kidney. We therefore hypothesized that obesity would modulate the association between systolic blood pressure (sBP) and albuminuria. Methods. The relationship between obesity and albuminuria [fractional albumin excretion (FE alb ) or albumin:creatinine ratio (ACR)] was modelled using linear/logistic regression in the US National Health and Nutrition Examination Survey 1999-2010 cohorts (N=23 710). Associations between sBP and albuminuria were examined across strata of waist circumference and body mass index (BMI) using interaction terms. Results. Obesity was associated with albuminuria through an interaction with sBP. Among participants in the 4th/5th quintiles of waist circumference each 10mmHg increase in sBP was accompanied by approximately double the increment in FE alb observed among those in quintile 2 (14% versus 7%, P<0.001). There was also evidence of a lower sBP threshold for the relationship between sBP and albuminuria in obesity. While FE alb increased with sBP>110mmHg in quintile 5 of waist circumference, in quintile 2 FE alb did not increase until sBP was >130mmHg. Findings were consistent when defining obesity by BMI or waist circumference and when quantifying albuminuria by ACR or FE alb . Assessing albuminuria as the odds ratio of ACR>30mg/g also gave similar results. Conclusion. The interaction between sBP and obesity supports the premise that obesity sensitizes the kidney to increased systemic blood pressure.