Body Mass Index Is Associated With Hospital Mortality in Critically Ill Patients: An Observational Cohort Study

Objective:Obesity is associated with a variety of diseases, which results in a decreased overall life expectancy. Nevertheless, some studies suggest that being overweight may reduce hospital mortality of certain patient groups, referred to as obesity paradox. Conflicting results for critically ill patients are reported. Therefore, we wished to investigate the association of body mass index and hospital mortality in critically ill patients. Design:Observational cohort study in Dutch critically ill patients. Setting:A dataset from the Dutch National Intensive Care Evaluation registry that includes patients admitted to Dutch ICUs was used. Patients:One hundred fifty-four thousand three hundred and eight ICU patients of teaching and nonteaching units in urban and nonurban hospitals. Interventions:None. Measurements and Main Results:We used logistic regression analysis, correcting for case mix (Simplified Acute Physiology Score II, age, gender, admission type, neoplasm, AIDS, hematologic malignancy, immunologic insufficiency, mechanical ventilation, and calendar year), to determine the relationship between body mass index and hospital mortality. Body mass index was included in the model as a continuous nonlinear covariate in a restricted regression spline transformation. To facilitate interpretation, adjusted odds ratios were calculated for the World Health Organization-based body mass index classes. Body mass index was found to be significantly associated with hospital mortality, with risks quickly increasing for underweight patients (body mass index < 18.5 kg/m2). Obese and seriously obese patients, with a body mass index of 30–39.9 kg/m2, had the lowest risk of death with an adjusted odds ratio of 0.86 (0.83–0.90). Conclusions:This large observational database shows an inverse association between obesity and hospital mortality in critically ill patients that could not be explained by a variety of known confounders.

[1]  G. Karkavelas,et al.  Diaphragmatic Adaptation Following Intra-abdominal Weight Charging , 2011, Obesity surgery.

[2]  G. Karkavelas,et al.  The Effects of Chronically Increased Intra-abdominal Pressure on the Rabbit Diaphragm , 2012, Obesity Surgery.

[3]  V. Montori,et al.  Association of bodyweight with total mortality and with cardiovascular events in coronary artery disease: a systematic review of cohort studies , 2006, The Lancet.

[4]  Giovanni Filardo,et al.  Categorizing BMI may lead to biased results in studies investigating in-hospital mortality after isolated CABG. , 2007, Journal of clinical epidemiology.

[5]  G. Steinberg.  Inflammation in Obesity is a Common Link Between Defects in Fatty Acid Metabolism and Insulin Resistance , 2007, Cell cycle.

[6]  G. Fonarow,et al.  An obesity paradox in acute heart failure: analysis of body mass index and inhospital mortality for 108,927 patients in the Acute Decompensated Heart Failure National Registry. , 2007, American heart journal.

[7]  K. Reinhart,et al.  The obesity paradox in surgical intensive care unit patients , 2011, Intensive Care Medicine.

[8]  M. Schulze,et al.  General and abdominal adiposity and risk of death in Europe. , 2008, The New England journal of medicine.

[9]  E. Villamor,et al.  Obesity and Mortality in Critically Ill Adults: A Systematic Review and Meta‐analysis , 2008, Obesity.

[10]  Andrew J S Coats,et al.  Body mass and survival in patients with chronic heart failure without cachexia: the importance of obesity. , 2003, Journal of cardiac failure.

[11]  Lauren Lissner,et al.  Hip circumference and cardiovascular morbidity and mortality in men and women. , 2004, Obesity research.

[12]  N F de Keizer,et al.  External validation of prognostic models for critically ill patients required substantial sample sizes. , 2007, Journal of clinical epidemiology.

[13]  R. Collins,et al.  Body-mass index and cause-specific mortality in 900 000 adults: collaborative analyses of 57 prospective studies , 2009, The Lancet.

[14]  June Stevens,et al.  Commentary: obesity claims and controversies. , 2006, International journal of epidemiology.

[15]  G. Fantuzzi.  Adipose tissue, adipokines, and inflammation. , 2005, The Journal of allergy and clinical immunology.

[16]  Jiguo Cao,et al.  An S-Plus function to calculate relative risks and adjusted means for regression models using natural splines , 2006, Comput. Methods Programs Biomed..

[17]  N. Lakkis,et al.  The obesity paradox: fact or fiction? , 2006, The American journal of cardiology.

[18]  S. Anker,et al.  The endotoxin-lipoprotein hypothesis , 2000, The Lancet.

[19]  K. Kalantar-Zadeh,et al.  Survival advantages of obesity in dialysis patients. , 2005, The American journal of clinical nutrition.

[20]  G. Fonarow,et al.  CARDIOVASCULAR AND SURVIVAL PARADOXES IN DIALYSIS PATIENTS: Reverse Epidemiology beyond Dialysis Patients: Chronic Heart Failure, Geriatrics, Rheumatoid Arthritis, COPD, and AIDS , 2007, Seminars in dialysis.

[21]  Frank E. Harrell,et al.  Regression Modeling Strategies: With Applications to Linear Models, Logistic Regression, and Survival Analysis , 2001 .

[22]  Obesity is associated with neutrophil dysfunction and attenuation of murine acute lung injury. , 2012, American journal of respiratory cell and molecular biology.

[23]  A. E. El Solh,et al.  Effect of obesity on intensive care morbidity and mortality: A meta-analysis* , 2008, Critical care medicine.

[24]  P. Pronovost,et al.  The impact of obesity on outcomes after critical illness: a meta-analysis , 2009, Intensive Care Medicine.

[25]  N. D. de Keizer,et al.  Quality of data collected for severity of illness scores in the Dutch National Intensive Care Evaluation (NICE) registry , 2002, Intensive Care Medicine.

[26]  M. Mazumdar,et al.  Mortality of Patients With Respiratory Insufficiency and Adult Respiratory Distress Syndrome After Surgery , 2012, Journal of intensive care medicine.