title: Body mass index is associated with hospital mortality in critically ill patients: an observational cohort study.
abstract: OBJECTIVE
  Obesity is associated with a variety of diseases, which results in a decreased overall life expectancy. Nevertheless, some studies suggest that being overweight may reduce hospital mortality of certain patient groups, referred to as obesity paradox. Conflicting results for critically ill patients are reported. Therefore, we wished to investigate the association of body mass index and hospital mortality in critically ill patients.
  
  
  METHODS
  Observational cohort study in Dutch critically ill patients.
  
  
  METHODS
  A dataset from the Dutch National Intensive Care Evaluation registry that includes patients admitted to Dutch ICUs was used.
  
  
  METHODS
  One hundred fifty-four thousand three hundred and eight ICU patients of teaching and nonteaching units in urban and nonurban hospitals.
  
  
  METHODS
  None.
  
  
  RESULTS
  We used logistic regression analysis, correcting for case mix (Simplified Acute Physiology Score II, age, gender, admission type, neoplasm, AIDS, hematologic malignancy, immunologic insufficiency, mechanical ventilation, and calendar year), to determine the relationship between body mass index and hospital mortality. Body mass index was included in the model as a continuous nonlinear covariate in a restricted regression spline transformation. To facilitate interpretation, adjusted odds ratios were calculated for the World Health Organization-based body mass index classes. Body mass index was found to be significantly associated with hospital mortality, with risks quickly increasing for underweight patients (body mass index < 18.5 kg/m). Obese and seriously obese patients, with a body mass index of 30-39.9 kg/m, had the lowest risk of death with an adjusted odds ratio of 0.86 (0.83-0.90).
  
  
  CONCLUSIONS
  This large observational database shows an inverse association between obesity and hospital mortality in critically ill patients that could not be explained by a variety of known confounders.
authors.affiliation: Department of Intensive Care, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands. p.pickkers@ic.umcn.nl
authors.forename: Peter
authors.initials: P
authors.lastname: Pickkers
authors.forename: Nicolette
authors.initials: N
authors.lastname: de Keizer
authors.forename: Joost
authors.initials: J
authors.lastname: Dusseljee
authors.forename: Daan
authors.initials: D
authors.lastname: Weerheijm
authors.forename: Johannes G
authors.initials: JG
authors.lastname: van der Hoeven
authors.forename: Niels
authors.initials: N
authors.lastname: Peek
mesh_terms: D000368:Aged; D015992:Body Mass Index; D015331:Cohort Studies; D016638:Critical Illness / Q000401:mortality*; D005260:Female; D017052:Hospital Mortality; D006801:Humans; D007362:Intensive Care Units; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009426:Netherlands / Q000453:epidemiology; D009765:Obesity / Q000401:mortality; D012042:Registries; D013851:Thinness / Q000401:mortality