BMI and Six‑Month Outcomes After Burn Injury

BMI category was associated with different 180-day outcomes after adult burn injury in a propensity-matched, real-world analysis.

Underweight status was linked to higher mortality and higher rates of several complications during follow-up, while overweight and obesity were associated with higher survival overall. The authors also reported that obesity was associated with a higher rate of skin and subcutaneous tissue infections.

Investigators identified adult patients with burn injury diagnoses in the TriNetX Research Network and required a documented BMI recorded from three months to one day prior to the index burn event; BMI values on the day of burn were excluded to avoid resuscitation-related distortion. Patients were categorized as underweight (BMI < 18.4 kg/m²), normal weight (18.5–24.9), overweight (25.0–29.9), or obese (≥30) per the study’s WHO-based definitions, and outcomes were captured for 180 days after the burn diagnosis. Across four independent pairwise analyses, cohorts were matched 1:1 on age, sex, race/ethnicity, total body surface area (TBSA), and smoke inhalation.

In the matched underweight versus normal-weight comparison, the authors report higher 180-day mortality among underweight patients, with absolute mortality of 0.06% versus 0.03% and an RR of 1.99 (95% CI, 1.73–2.287) and HR of 2.01 (95% CI, 1.746–2.320). Over the same follow-up window, the propensity-matched analysis linked underweight status to higher risks of sepsis, pneumonia, cardiovascular events, and psychological impairment versus normal weight.

For comparisons of higher BMI categories versus normal weight, investigators report lower 180-day mortality risk ratios for both overweight (RR 0.74) and obesity (RR 0.71). They also describe generally lower risks for several complications in the overweight and obese cohorts versus normal weight, though the specific profile varied by outcome and comparison. Within that overall pattern, obesity was reported to be associated with increased skin or subcutaneous tissue infections (RR 1.14) compared with normal weight.

In discussing these results, the authors frame the observed survival advantage for higher BMI categories as consistent with an “obesity paradox” in burn outcomes and describe BMI as a potential component within multidimensional risk stratification alongside other clinical factors. They also highlight limitations tied to real-world coding and platform constraints, including incomplete or variably coded TBSA, residual confounding (including comorbidity-related confounding), and the TriNetX restriction to pairwise comparisons. In addition, they report that outcomes could not be cleanly separated into in-hospital versus post-discharge events over the 180-day window.