Non Linear Relationship between BMI and Sepsis among ICU Patients: Analysis of the MIMIC-III Real World Database

Introduction: The relationship between occurrence of sepsis and Body Mass Index (BMI) has been studied by treating BMI as a categorical variable based on the standard categories developed by the World Health Organisation (WHO). This technique masks the actual form of the relationship that exist between BMI and sepsis. Aim: To determine the shape of the association between BMI and probability of sepsis after adjusting the effect of gender, age, ethnicity and co-morbidities among critically-ill patients and to identify an appropriate technique to elucidate this association. Materials and Methods: The study was based on the data extracted from the Medical Information Mart for Intensive Care III (MIMIC-III) database, a real-world dataset. A robust Poisson regression model and a Restricted Cubic Spline (RCS) regression model were applied to model the data. Results: The study revealed a non linear relationship between BMI and occurrence of sepsis. From the RCS plot, an increased risk of sepsis was observed among underweight and obese males and a similar pattern was observed among those with hypertension. BMI, age, and hypertension were found to be significant in the robust Poisson model (RR 1.01, 95% CI 1.00-1.02, RR 1.01, 95% CI 1.00- 1.02, and RR 0.76, 95% CI 0.69-0.84, p