Obesity-related excess mortality rate in an adult intensive care unit: A risk-adjusted matched cohort study*

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Abstract
Objective To evaluate the obesity-related mortality rate in an intensive care unit. Design An exposed/unexposed matched cohort study. Setting An 18-bed adult medical-surgical intensive care unit in a 1,100-bed regional and teaching hospital in France. Patients From January 1, 1999, to December 31, 2001, 170 mechanically ventilated exposed patients (obese patients with body mass index of >30 kg/m2) were matched with 170 mechanically ventilated unexposed patients (with ideal body mass index of 18.5–24.9 kg/m2). Interventions None. Measurements and Main Results The matching process was conducted according to eight criteria: cause of admission, indication for ventilatory support, immunologic status, cardiac status, probability of death (±5%), age (±7 yrs), gender, and acquisition of severe events appearing within 24 hrs before admission (defined as resuscitated cardiac arrest, acute respiratory distress syndrome, or septic shock). The mortality rate between exposed and unexposed patients was compared by univariate analysis and then was adjusted for other possible confounding factors by multivariate analysis, using conditional logistic regression. The matching process was successful for 1,360 of 1,360 criteria. Obesity was significantly associated with intensive care unit mortality (odds ratio, 2.1; 95% confidence interval, 1.2–3.6). Obesity-related excess mortality was verified mainly for the youngest patients (odds ratio, 2.5; 95% confidence interval, 1.6–6.1) and for the patients with a probability of intensive care unit death of 11–50% (odds ratio, 2.6; 95% confidence interval, 1.2–5.5). This excess mortality rate could be explained by the higher risk of intensive care unit acquired complications among obese patients than among the unexposed ones (odds ratio, 4; 95% confidence interval, 1.4–11.8). Conclusions Obesity is an independent risk factor for intensive care unit death and should be regarded as a severe comorbidity in such units.