The Influence of BMI on Mortality and Clinical Outcomes After Burns

Background: Weight extremes are linked to morbidity, yet their impact on burn outcomes remains underinvestigated. Prior studies suggest an ‘obesity paradox’, showing survival benefits and better functional outcomes in obese patients. Methods: This study used the global real-world database TriNetX to assess the association between body mass index (BMI) and clinical outcomes in adult burn patients, categorized using WHO definitions. After 1:1 propensity score matching for demographics, burn severity, and smoke inhalation injury, clinical outcomes were analyzed over a six-month period following burn injury. Outcomes included mortality, sepsis, pneumonia, acute kidney injury (AKI), cardiovascular events, graft complications, skin infections, and psychological impairment. Results: After matching, 9736 patients were included in the underweight versus normal weight comparison, 72,274 in overweight versus normal weight, 71,195 in obesity versus normal weight, and 9732 in underweight versus obesity. Underweight patients were associated with higher mortality and increased risks of sepsis, pneumonia, cardiovascular events, and psychological impairment. Overweight and obese patients showed higher survival rates and overall better clinical outcome associations. Conclusions: These findings are consistent with the previously described ‘obesity paradox’ in burn care and identify underweight burn patients as a distinct high-risk subgroup.