The effect of obesity on 12-month survival following admission to intensive care: a prospective study

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. DESIGN: Prospective, observational cohort study. SETTING: Fourteen-bed medical and surgical ICU of a university-affiliated hospital. PATIENTS: Four hundred and ninety-three adult patients. INTERVENTIONS: None. MEASUREMENTS AND MAIN 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.