title: Effect of age and dialysis vintage on obesity paradox in long-term hemodialysis patients.
abstract: BACKGROUND
  In contrast to the general population, higher body mass index (BMI) is associated with greater survival in patients receiving hemodialysis (HD; "obesity paradox"). We hypothesized that this paradoxical association between BMI and death may be modified by age and dialysis vintage.
  
  
  METHODS
  Retrospective observational study using a large HD patient cohort.
  
  
  METHODS
  123,383 maintenance HD patients treated in DaVita dialysis clinics between July 1, 2001, and June 30, 2006, with follow-up through September 30, 2009.
  
  
  METHODS
  Age, dialysis vintage, and time-averaged BMI. Time-averaged BMI was divided into 6 subgroups; <18.5, 18.5-<23.0, 23.0-<25.0, 25.0-<30.0, 30.0-<35.0, and ≥35.0kg/m(2). BMI category of 23-<25kg/m(2) was used as the reference category.
  
  
  RESULTS
  All-cause, cardiovascular, and infection-related mortality.
  
  
  RESULTS
  Mean BMI of study participants was 27±7kg/m(2). Time-averaged BMI was <18.5 and ≥35kg/m(2) in 5% and 11% of patients, respectively. With progressively higher time-averaged BMI, there was progressively lower all-cause, cardiovascular, and infection-related mortality in patients younger than 65 years. In those 65 years or older, even though overweight/obese patients had lower mortality compared with underweight/normal-weight patients, sequential increases in time-averaged BMI > 25kg/m(2) added no additional benefit. Based on dialysis vintage, incident HD patients had greater all-cause and cardiovascular survival benefit with a higher time-averaged BMI compared with the longer term HD patients.
  
  
  CONCLUSIONS
  Causality cannot be determined, and residual confounding cannot be excluded given the observational study design.
  
  
  CONCLUSIONS
  Higher BMI is associated with lower death risk across all age and dialysis vintage groups. This benefit is more pronounced in incident HD patients and those younger than 65 years. Given the robustness of the survival advantage of higher BMI, examining interventions to maintain or even increase dry weight in HD patients irrespective of age and vintage are warranted.
authors.affiliation: Harold Simmons Center for Kidney Disease Research and Epidemiology, University of California Irvine, School of Medicine, Orange, CA.
authors.forename: Tania
authors.initials: T
authors.lastname: Vashistha
authors.affiliation: Division of Nephrology, University of Washington, Seattle, WA.
authors.forename: Rajnish
authors.initials: R
authors.lastname: Mehrotra
authors.affiliation: Harold Simmons Center for Kidney Disease Research and Epidemiology, University of California Irvine, School of Medicine, Orange, CA; Division of Nephrology, Ulsan University Hospital, University of Ulsan College of Medicine, Ulsan, South Korea.
authors.forename: Jongha
authors.initials: J
authors.lastname: Park
authors.affiliation: Harold Simmons Center for Kidney Disease Research and Epidemiology, University of California Irvine, School of Medicine, Orange, CA.
authors.forename: Elani
authors.initials: E
authors.lastname: Streja
authors.affiliation: Division of Nephrology and Hypertension, Harbor-UCLA Medical Center, Torrance.
authors.forename: Ramnath
authors.initials: R
authors.lastname: Dukkipati
authors.affiliation: DaVita Inc, El Segundo, CA.
authors.forename: Allen R
authors.initials: AR
authors.lastname: Nissenson
authors.affiliation: Department of Public Health Sciences, University of Virginia, Charlottesville, VA.
authors.forename: Jennie Z
authors.initials: JZ
authors.lastname: Ma
authors.affiliation: Division of Nephrology, University of Tennessee Health Science Center, Memphis, TN; Division of Nephrology, Memphis VA Medical Center, Memphis, TN.
authors.forename: Csaba P
authors.initials: CP
authors.lastname: Kovesdy
authors.affiliation: Harold Simmons Center for Kidney Disease Research and Epidemiology, University of California Irvine, School of Medicine, Orange, CA; Fielding School of Public Health at UCLA, Los Angeles, CA. Electronic address: kkz@uci.edu.
authors.forename: Kamyar
authors.initials: K
authors.lastname: Kalantar-Zadeh
mesh_terms: D000367:Age Factors; D000368:Aged; D015992:Body Mass Index; D002318:Cardiovascular Diseases / Q000401:mortality / Q000503:physiopathology; D005260:Female; D006801:Humans; D007676:Kidney Failure, Chronic / Q000453:epidemiology / Q000401:mortality* / Q000628:therapy; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000453:epidemiology / Q000401:mortality* / Q000503:physiopathology; D006435:Renal Dialysis / Q000401:mortality*; D012189:Retrospective Studies; D016019:Survival Analysis
keywords: BMI; ESRD; Obesity-mortality paradox; hemodialysis; mortality risk