title: Influence of body mass index on the association of weight changes with mortality in hemodialysis patients.
abstract: OBJECTIVE
  A high body mass index (BMI) is associated with lower mortality in patients undergoing hemodialysis. Short-term weight gains and losses are also related to lower and higher mortality risk, respectively. The implications of weight gain or loss may, however, differ between obese individuals and their nonobese counterparts.
  
  
  METHODS
  The Current Management of Secondary Hyperparathyroidism: A Multicenter Observational Study (COSMOS) is an observational study including 6797 European hemodialysis patients recruited between February 2005 and July 2007, with prospective data collection every 6 months for 3 years. Time-dependent Cox proportional hazard regressions assessed the effect of BMI and weight changes on mortality. Analyses were performed after patient stratification according to their starting BMI.
  
  
  RESULTS
  Among 6296 patients with complete data, 1643 died. At study entry, 42% of patients had a normal weight (BMI, 20-25 kg/m(2)), 11% were underweight, 31% were overweight, and 16% were obese (BMI ≥ 30 kg/m(2)). Weight loss or gain (<1% or >1% of body weight) was strongly associated with higher rates of mortality or survival, respectively. After stratification by BMI categories, this was true in nonobese categories and especially in underweight patients. In obese patients, however, the association between weight loss and mortality was attenuated (hazard ratio, 1.28 [95% confidence interval (CI), 0.74 to 2.14]), and no survival benefit of gaining weight was seen (hazard ratio, 0.98 [95% CI, 0.59 to 1.62]).
  
  
  CONCLUSIONS
  Assuming that these weight changes were unintentional, our study brings attention to rapid weight variations as a clinical sign of health monitoring in hemodialysis patients. In addition, a patient's BMI modifies the strength of the association between weight changes with mortality.
authors.affiliation: Due to the number of contributing authors, the affiliations are provided in the Supplemental Material.
authors.forename: Iván
authors.initials: I
authors.lastname: Cabezas-Rodriguez
authors.forename: Juan Jesús
authors.initials: JJ
authors.lastname: Carrero
authors.forename: Carmine
authors.initials: C
authors.lastname: Zoccali
authors.forename: Abdul Rashid
authors.initials: AR
authors.lastname: Qureshi
authors.forename: Markus
authors.initials: M
authors.lastname: Ketteler
authors.forename: Jürgen
authors.initials: J
authors.lastname: Floege
authors.forename: Gérard
authors.initials: G
authors.lastname: London
authors.forename: Francesco
authors.initials: F
authors.lastname: Locatelli
authors.forename: José Luis
authors.initials: JL
authors.lastname: Gorriz
authors.forename: Boleslaw
authors.initials: B
authors.lastname: Rutkowski
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Memmos
authors.forename: Anibal
authors.initials: A
authors.lastname: Ferreira
authors.forename: Adrian
authors.initials: A
authors.lastname: Covic
authors.forename: Vladimir
authors.initials: V
authors.lastname: Teplan
authors.forename: Willem-Jan
authors.initials: WJ
authors.lastname: Bos
authors.forename: Reinhard
authors.initials: R
authors.lastname: Kramar
authors.forename: Drasko
authors.initials: D
authors.lastname: Pavlovic
authors.forename: David
authors.initials: D
authors.lastname: Goldsmith
authors.forename: Judit
authors.initials: J
authors.lastname: Nagy
authors.forename: Miha
authors.initials: M
authors.lastname: Benedik
authors.forename: Dierik
authors.initials: D
authors.lastname: Verbeelen
authors.forename: Christian
authors.initials: C
authors.lastname: Tielemans
authors.forename: Rudolf P
authors.initials: RP
authors.lastname: Wüthrich
authors.forename: Pierre-Yves
authors.initials: PY
authors.lastname: Martin
authors.forename: Carlos
authors.initials: C
authors.lastname: Martínez-Salgado
authors.forename: José Luis
authors.initials: JL
authors.lastname: Fernández-Martín
authors.forename: Jorge B
authors.initials: JB
authors.lastname: Cannata-Andia
mesh_terms: D000328:Adult; D000368:Aged; D015992:Body Mass Index; D001835:Body Weight; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D011446:Prospective Studies; D006435:Renal Dialysis / Q000401:mortality*