Body Mass Index (BMI) and mortality in patients with severe burns: Is there a "tilt point" at which obesity influences outcome?

Background: Obesity is a serious health hazard. Despite advances in burn care severely obese patients with large burns have higher mortality compared with normal-weight patients. The Body Mass Index is the universal measure to define and classify obesity. This study aims to evaluate the effect of Body Mass Index (BMI) on mortality of severe burn patients. Methods: A retrospective study of 95 patients treated over 2-year period in a dedicated burn ITU. Mortality was studied in relation to BMI as well as demographic, burn characteristics well as length of hospital stay. Logistic regression model and non-parametric comparison tests were used for analysis. Results: Mean age was 42 ± 22 years (mean ± SD), Total Burn Surface area (TBSA) 33 ± 16%, BMI 29 ± 7.5 (kg/m ²) and hospital stay was 37 ± 33 days. Incidence of inhalation injury was 29% and over all mortality was 19%. By logistic regression age, TBSA and inhalation injury were separately associated with mortality. Patients with BMI ≥ 35 (kg/m ²) had significantly higher mortality compared with patients with BMI < 25 (kg/m ²) [p = 0.037 (Fisher's exact test)]. Conclusions: Body Mass Index ≥ 35 (kg/m ²) is a tilt point, which is associated with a higher than predicted mortality following burns when compared to burned patients with a normal BMI.