title: The impact of body mass index on renal transplant outcomes: a significant independent risk factor for graft failure and patient death.
abstract: BACKGROUND
  Renal transplant recipients with elevated body mass index (BMI) have been shown to have inferior patient survival as compared to patients with lower BMI. However, previous studies could not establish a link between increased BMI and decreased death censored graft survival. Obesity in nontransplant patients has been associated with hypertension, hyperlipidemia, type II diabetes, proteinuria and glomerulopathy. Given this evidence it is possible that renal transplant recipients with an elevated BMI may have worse long term graft survival. To investigate this hypothesis we retrospectively analyzed 51,927 primary, adult renal transplants registered in the USRDS.
  
  
  METHODS
  BMI at date of transplant was calculated for all patients using BMI=body weight (in kg)=.stature (height, in meters) squared. BMI values were further categorized into 11 categories: below 18, from 18 to 36 at 2 unit increments, and above 36 kg/m2. Primary study end points were graft and patient survival. Secondary study end points were death censored graft survival, chronic allograft failure, delayed graft function, and acute rejection (AR). Cox proportional hazard and logistic regression models investigated the link between categorized BMI and the study end points correcting for potential confounding variables.
  
  
  RESULTS
  BMI showed a very strong association with outcomes after renal transplantation. The extremes of very high and very low BMI were associated with significantly worse patient and graft survival. The same was true for death censored graft survival and chronic allograft failure. Elevated BMI was also associated with an increased risk for delayed graft function while lower BMI was significantly protective. Acute rejection did not show any significant association with BMI.
  
  
  CONCLUSIONS
  BMI has a very strong association with outcomes after renal transplantation independent of most of the known risk factors for patient and graft survival. The extremes of very high and very low BMI before renal transplantation are important risk factors for patient and graft survival. It is important to note that elevated BMI was significantly associated with worse graft survival independent of patient survival. Whether prospective weight adjustment before renal transplantation can favorably affect posttransplant risk needs to be assessed by further studies.
authors.affiliation: Division of Nephrology, University of Florida, Shands Hospital, 1600 SW Archer Rd., RM CG-98, Gainesville FL 32610-0224, USA. meierhu@medicine.ufl.edu
authors.forename: Herwig-Ulf
authors.initials: HU
authors.lastname: Meier-Kriesche
authors.forename: Julie A
authors.initials: JA
authors.lastname: Arndorfer
authors.forename: Bruce
authors.initials: B
authors.lastname: Kaplan
mesh_terms: D000328:Adult; D015992:Body Mass Index; D006801:Humans; D016030:Kidney Transplantation / Q000401:mortality* / Q000473:pathology / Q000502:physiology*; D016016:Proportional Hazards Models; D012044:Regression Analysis; D012189:Retrospective Studies; D012306:Risk; D012307:Risk Factors; D015996:Survival Rate; D017211:Treatment Failure; D016896:Treatment Outcome