324 Impact of Body Mass Index on the Outcome of Polytrauma Patients: An Inverse Probability Treatment Weight Analysis

INTRODUCTION: Polytrauma is a condition that involves multiple injuries affecting different organ systems. Although Body Mass Index (BMI) is generally associated with health outcomes across various diseases, the recent concept of “obesity paradox” suggests that higher BMI might be protective in certain conditions. However, the relationship between BMI and polytrauma-related mortality remains unclear due to conflicting study results. METHODS: A retrospective study was conducted on 1234 adult patients with critical polytrauma admitted to one Level 1 trauma center from Jan. 2011 to Dec. 2019. The primary outcomes were 30-day and 365-day all-cause mortality, while the secondary outcome was length of hospital stay. Statistical analysis was performed using IPTW and Cox proportional-hazard models to assess the impact of BMI on mortality, with subgroup analyses examining age, gender, intracerebral hemorrhage (ICH) status, and injury severity score factors. RESULTS: The 30-day mortality rates were 7.5%, 8.2%, 2.4%, and 2.6% for underweight, normal weight, overweight, and obese groups, respectively, while the 365-day mortality rates were 12.5%, 14.2%, 7.5%, and 7.7%, respectively. IPTW-weighted Cox regression analysis indicated that only overweight had a significant 30-day (HR=0.21, p<0.05) and 365-day (HR=0.57, p<0.05) survival advantages compared to the normal weight. Although obesity did not demonstrate benefits in short-term and long-term survival, it was significantly associated with shorter lengths of hospital stays compared to the normal weight group (3.56 vs. 10.58 days, p<0.001). In subgroup analyses, the protective effect of being overweight on mortality outcomes was more pronounced in polytrauma patients who were very old, male, without ICH, and had severe trauma. The spline curve analysis revealed a non-linear relationship between BMI and mortality risk. CONCLUSIONS: The “obesity paradox” might offer a survival advantage in polytrauma patients, particularly for the overweight group, while obese patients have shorter hospital stays.