title: Increased body mass index may be associated with greater risk of end-stage renal disease in whites compared to blacks: A nested case-control study.
abstract: BACKGROUND
  The relationship between body mass index (BMI) and end-stage renal disease (ESRD) may differ between blacks and whites due to underlying metabolic differences.
  
  
  METHODS
  We conducted a nested case-control study of 631 incident ESRD cases and 1,897 matched controls within the Southern Community Cohort Study. Current weight, height, and weight at age 21 were reported at enrollment. Occurrence of ESRD was ascertained by linkage with the United States Renal Data System. With normal BMI (18.5-24.9 kg/m2) as reference, conditional logistic regression was used to calculate adjusted odds ratios (OR) and corresponding 95% confidence intervals (CI) for ESRD across other BMI categories by race. In subsequent analysis, BMI at age 21 was modeled using restricted cubic splines with 5 knots. Predicted probabilities of incident ESRD were computed from the multivariable logistic models and plotted against BMI at age 21.
  
  
  RESULTS
  Among blacks, odds of ESRD were significantly increased among those who were overweight (OR: 1.41; 95%CI: 1.09, 1.83) or obese (OR: 2.56; 95%CI: 1.88, 3.47) at age 21. Among whites, the association between ESRD and BMI at age 21 was more pronounced, with corresponding ORs of 2.13 (95%CI: 0.92, 4.93) and 7.46 (95%CI: 2.90, 19.21; p-interaction 0.05). Only among whites was high BMI at enrollment associated with ESRD risk; OR for BMI≥40 kg/m2, was 3.31 (95%CI: 1.08, 10.12). The plot of the predicted probabilities of incident ESRD vs BMI at age 21 showed a monotonic increase in the probability of ESRD after a BMI cutoff ≈ 25Kg/m2in both whites and blacks but the slope of the curve for whites appeared greater.
  
  
  CONCLUSIONS
  Our results suggest racial differences in the relationship between BMI, both in early adulthood and middle age, and ESRD. These findings warrant further research into understanding the underlying metabolic differences that may explain these differences.
authors.affiliation: Division of Epidemiology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA.
authors.forename: Elvis A
authors.initials: EA
authors.lastname: Akwo
authors.affiliation: Division of Nephrology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA; Vanderbilt Center for Kidney Disease, Vanderbilt University Medical Center, Nashville, Tennessee, USA.
authors.forename: Kerri L
authors.initials: KL
authors.lastname: Cavanaugh
authors.affiliation: Division of Nephrology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA; Vanderbilt Center for Kidney Disease, Vanderbilt University Medical Center, Nashville, Tennessee, USA.
authors.forename: Talat Alp
authors.initials: TA
authors.lastname: Ikizler
authors.affiliation: Division of Epidemiology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA; International Epidemiology Institute, Rockville, Maryland, USA.
authors.forename: William J
authors.initials: WJ
authors.lastname: Blot
authors.affiliation: Division of Epidemiology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tennessee, USA; Vanderbilt Center for Kidney Disease, Vanderbilt University Medical Center, Nashville, Tennessee, USA.
authors.forename: Loren
authors.initials: L
authors.lastname: Lipworth
keywords: Body mass index; blacks; end-stage renal disease; interaction; whites