Influence of body mass index on SAPS3 prognostic performance in critically ill patients from Brazil

Obesity has emerged as a significant global health problem, and its association with increased morbidity and mortality is well established. An obesity paradox has been extensively documented in the critically ill, appearing as a protective factor. Whether body mass index (BMI) impacts critical care severity scores has not been extensively studied previously, particularly in developing countries. This study aimed to evaluate the performance of severity scores across different BMI categories in a tertiary intensive care unit in Brazil. Observational and analytical cohort study in a general ICU in Northeastern Brazil between August 2015 and July 2018 that included all patients over 18 years of age admitted to the ICU. A total of 2,179 patients were included, with a mean age of 67.9 years and female predominance (53.1%). Similar to previous findings, those with overweight and obesity of any grade were not significantly associated with mortality, though for each additional 1kg/m2 there was a decrease of 0.04% in odds of death. The Simplified Acute Physiology Score III (SAPS3) accurately predicted mortality in all groups except in those underweight. Low weight appeared as an independent risk factor for mortality in the ICU. Furthermore, this is the first study to identify poor prognostic performance of a common ICU severity score in those with low weight, highlighting the need for alternative more precise metrics.