title: The effect of obesity on 12-month survival following admission to intensive care: a prospective study.
abstract: OBJECTIVE
  Evaluate the effect of intensive care (ICU) admission body mass index (BMI) on 30-day and 12-month survival in critically ill patients and determine the impact of obesity on outcome.
  
  
  METHODS
  Prospective, observational cohort study.
  
  
  METHODS
  Fourteen-bed medical and surgical ICU of a university-affiliated hospital.
  
  
  METHODS
  Four hundred and ninety-three adult patients.
  
  
  METHODS
  None.
  
  
  RESULTS
  BMI (kg/m) was calculated from height (m) and measured weight (kg) within 4 hrs of ICU admission, using the PROMED weighing device, or premorbid weight (documented in the previous month) (BMImeasured). Follow-up was for >/=12 months post-ICU admission. Time to mortality outcome, censored at 30 and 365 days (12-months), was analyzed using a log-normal accelerated failure time regression model. Predictor variables were parameterized as time ratios (TR), where TR <1 is associated with decreased survival time and TR >1 is associated with prolonged survival time. Mean (sd) age and Acute Physiology and Chronic Health Evaluation II score were 62.3 (17.5) years and 20.7(8.4), respectively; 56.0% (285 of 493) of patients were male and 60.6% (299 of 493) medical. ICU admission weight and BMImeasured (available in 433 patients) were 79.1 (22.1) kg and 27.8 (7.0) kg/m, respectively. In 16.9% (73 of 433) of patients, weight was >/=100 kg, and in 29.8% (129 of 433), BMImeasured was >/=30 kg/m. Raw intensive care, 30-day, and 12-month mortality rates were 15.2% (66 of 433), 22.3% (95 of 433), and 37.3% (159 of 433), respectively. BMImeasured was a significant determinant of mortality at 30 days (TR 1.853, 95% confidence interval 1.053-3.260, p = .032) and 12 months (TR 1.034, 95% confidence interval 1.005-1.063, p = .019). The effect of BMI on 12-month mortality was linear, such that increasing BMI was associated with decreasing mortality.
  
  
  CONCLUSIONS
  ICU admission BMI was a determinant of short- to medium-term survival. Obesity was not associated with adverse outcomes and may be protective.
authors.affiliation: Department of Intensive Care Medicine, The Queen Elizabeth Hospital, Woodville, South Australia, Australia. sandra.peake@nwahs.sa.gov.au
authors.forename: Sandra L
authors.initials: SL
authors.lastname: Peake
authors.forename: John L
authors.initials: JL
authors.lastname: Moran
authors.forename: Dhaval R
authors.initials: DR
authors.lastname: Ghelani
authors.forename: Amanda J
authors.initials: AJ
authors.lastname: Lloyd
authors.forename: Michaela J
authors.initials: MJ
authors.lastname: Walker
mesh_terms: D015992:Body Mass Index; D016638:Critical Illness / Q000401:mortality*; D005260:Female; D006760:Hospitalization; D006785:Hospitals, University; D006801:Humans; D007362:Intensive Care Units / Q000706:statistics & numerical data*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications*; D011446:Prospective Studies; D015996:Survival Rate