The role of body weight in burn mortality

Burn injuries are a major global health problem, and body mass index (BMI) has been associated with mortality risk in burn patients aged 18 years and older. Although studies have suggested that higher weight may elevate mortality due to the presence of comorbidities, the independent role of BMI in burn outcomes among adult patients remains unclear.

This retrospective cohort study analysed data from the TriNetX database for 248,768 burn patients aged 18 years and older, with data collected up to September 1, 2025, segmented by total body surface area (TBSA) burns (<10% or ≥10%) and BMI. Propensity score matching was used to adjust for age, sex, race, ethnicity, and comorbidities. Hazard ratios (HRs) for mortality were calculated using Cox regression analysis.

Among burn patients with < 10% TBSA involvement, the underweight group (BMI <18.5) had the highest mortality risk (HR 1.27, 95% CI: 1.114-1.349) compared with the normal BMI group (BMI 18.5-24.9). Reduced mortality risks were observed in the overweight (HR 0.85, 95% CI: 0.801-0.891), obesity class I (HR 0.78, 95% CI: 0.736-0.826), and obesity class II groups (HR 0.79, 95% CI: 0.734-0.843). Obesity class III (HR 0.94, 95% CI: 0.864-1.019) showed no statistically significant difference. In patients with burns ≥ 10% TBSA, the underweight group demonstrated the highest HR (1.04, 95% CI: 0.877-1.227), though not statistically significant. Lower risks were noted in the overweight (HR 0.86, 95% CI: 0.787-0.937), obesity class I (HR 0.78, 95% CI: 0.711-0.865), and obesity class II groups (HR 0.85, 95% CI: 0.751-0.966), while obesity class III (HR 0.99, 95% CI: 0.852-1.151) did not differ significantly from the reference group.

Although previous studies have linked higher BMI to increased burn mortality due to comorbidities, after adjustment for measured factors, overweight and class I and II obesity were associated with lower mortality compared with normal BMI.