Obesity is associated with increased morbidity but not mortality in critically ill patients

Objective: To investigate the possible impact of obesity on morbidity and mortality in intensive care unit (ICU) patients included in the European observational sepsis occurrence in acutely ill patients (SOAP) study. Design: Planned substudy from the SOAP database. Setting: One hundred and ninety-eight ICUs in 24 European countries. Patients: All patients admitted to one of the participating ICUs. Patients were classified, according to their body mass index (BMI), as underweight (< 18.5 kg/m(2)), normal weight (18.5-24.9 kg/m(2)), overweight (25-29.9 kg/m(2)), obese (30-39.9 kg/m(2)), and very obese (>= 40 kg/m(2)). Measurements and results: The BMI was available in 2,878 (91%) of the 3,147 patients included in the SOAP study; 120 patients (4.2%) were underweight, 1,206 (41.9%) had a normal BMI, 1,047 (36.4%) were overweight, 424 (14.7%) were obese, and 81 (2.8%) were very obese. Obese and very obese patients more frequently developed ICU-acquired infections than patients in lower BMI categories. Very obese patients showed a trend towards longer ICU [median (IQ): 4.1 (1.8-12.1) vs. 3.1 (1.7-7.2) days, P = 0.056) and hospital lengths of stay [14.3 (8.4-27.4) vs. 12.3 (5.1-24.4), days P = 0.077] compared to those with a normal BMI. However, there were no significant differences among the groups in ICU or hospital mortality rates. In a multivariate Cox regression analysis, none of the BMI categories was associated with an increased risk of 60-day in-hospital death. Conclusion: BMI did not have a significant impact on mortality in this mixed population of ICU patients.