title: Impact of body mass index on outcomes following critical care.
abstract: OBJECTIVE
  To determine the impact of body mass index (BMI) on outcomes in critically ill patients.
  
  
  METHODS
  Retrospective analysis of a large multi-institutional ICU database.
  
  
  METHODS
  The influence of BMI classification (underweight, < 20 kg/m(2); normal [control subjects], 20 to 25 kg/m(2); overweight, 25 to 30 kg/m(2); obese, 30 to 40 kg/m(2); severe obesity, > 40 kg/m(2)) on hospital survival, functional status at hospital discharge, and ICU/hospital length of stay (LOS) was analyzed via multivariate analysis, adjusting for age, gender, type of hospital admission, and severity score (ie, simplified acute physiologic score [SAPS] II and mortality prediction model [MPM] at time zero). Univariate analysis also was performed according to the quartile of the severity score. All comparisons were to the normal BMI group.
  
  
  RESULTS
  Of 63,646 patient datasets, 41,011 were complete for height, weight, and at least one of the two severity scores. We found increased mortality in underweight patients (odds ratio [OR] of death: SAPS group, 1.19; MPM group, 1.26) but not in overweight, obese, or severely obese patients. ICU and hospital LOS were increased in both the severely obese (OR of discharge: ICU, 0.81 and 0.84, respectively; hospital, 0.83 and 0.87, respectively) and underweight groups (OR of discharge: ICU, 0.96 and 0.94, respectively; hospital, 0.91 and 0.90, respectively). Only in the SAPS group did the obese group have increased ICU LOS (OR, 0.96) and hospital LOS (OR, 0.96). Functional status at discharge was impaired in underweight patients (OR of disability: ICU, 1.11; hospital, 1.19). Overweight patients had decreased discharge disability (OR of disability: SAPS, 0.93; MPM, 0.94), while the results in the obese group were discordant between the two severity score groups (SAPS, not significant; MPM, 0.91; p < 0.05 for all ORs).
  
  
  CONCLUSIONS
  Low BMI, but not high BMI, is associated with increased mortality and worsened hospital discharge functional status. LOS is increased in severely obese patients and, to a lesser extent, in underweight patients. Patients in the overweight and obese BMI groups may have improved mortality and discharge functional status.
authors.affiliation: Department of Pulmonary and Critical Care Medicine, Baylor College of Medicine, Houston, TX, USA. atrembla@ucalgary.ca
authors.forename: Alain
authors.initials: A
authors.lastname: Tremblay
authors.forename: Venkata
authors.initials: V
authors.lastname: Bandi
mesh_terms: D000328:Adult; D015992:Body Mass Index; D001835:Body Weight; D016638:Critical Illness / Q000401:mortality*; D005260:Female; D006305:Health Status Indicators; D017052:Hospital Mortality; D006801:Humans; D007902:Length of Stay; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D012189:Retrospective Studies; D012720:Severity of Illness Index