BMI is independently associated with ARDS, sepsis and Multiorgan Failure after major Trauma - results of a high-volume retrospective observational cohort study

Background Obesity is increasingly prevalent among trauma patients and has been proposed to influence post-injury inflammatory responses and organ dysfunction. However, evidence on the independent effect of body mass index (BMI) on in-hospital complications after major trauma remains conflicting. This study aimed to determine whether BMI is an independent predictor of specific adverse clinical outcomes in a large cohort of adult trauma patients. Methods This retrospective cohort study analyzed associations between BMI and adverse clinical outcomes (ARDS, pneumonia, sepsis, multiorgan failure (MOF) and mortality) among adult trauma patients at a German level-I trauma center between 2018 and 2024. Inclusion criteria were trauma leading to an Injury Severity Score (ISS) ≥ 9 and/or admission to the intensive care unit. Multivariable logistic regression adjusted for BMI, age, sex, ASA and ISS. Results A total of 1514 patients were included. Adjusted multivariate regression revealed BMI as being independently associated with an increased risk of ARDS (aOR 1.09 per kg/m², 95% CI 1.01–1.16; p = 0.020), sepsis (aOR 1.05, 95% CI 1.00–1.10; p = 0.048) and MOF (aOR 1.10, 95% CI 1.04–1.17; p < 0.001), but not with pneumonia or mortality. Categorical BMI analysis identified obesity (> 30 kg/m ² ) as a clinically relevant non-linear cut-off point. Conclusions Higher BMI is independently associated with ARDS, sepsis and MOF after major trauma. This highlights BMI as clinically relevant modifier of early post-traumatic organ dysfunction, and underscores the need for targeted monitoring strategies in obese trauma patients.