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

Peake, Sandra L. BM, BS, BSc (Hons), FJFICM, PhD; Moran, John L. MB, BS, FANZCA, FRACP, FJFICM; Ghelani, Dhaval R. MD, FJFICM; Lloyd, Amanda J. RN (ICU Cert); Walker, Michaela J. RN, B Nurs, Grad Dip (ICN)

doi: 10.1097/01.CCM.0000248726.75699.B1
Clinical Investigations
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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/m2) 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/m2, respectively. In 16.9% (73 of 433) of patients, weight was ≥100 kg, and in 29.8% (129 of 433), BMImeasured was ≥30 kg/m2. 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.

From the Department of Intensive Care Medicine, The Queen Elizabeth Hospital, Woodville, South Australia, Australia.

The authors have not disclosed any potential conflicts of interest.

Address requests for reprints to: Sandra L. Peake, BM, BS, BSc(Hons), FJFICM, PhD, Department of Intensive Care Medicine, the Queen Elizabeth Hospital, 28 Woodville Road, Woodville 5011, South Australia, Australia. E-mail: sandra.peake@nwahs.sa.gov.au

© 2006 by the Society of Critical Care Medicine and Lippincott Williams & Wilkins