Epidemiology and prognostic factors in older adults with severe burns (≥10% TBSA): A 13-year retrospective study from a French national burn center.

BACKGROUND

High mortality in older burn patients results from the combination of acute injury and physiological decline. While total body surface area burned (TBSA) and age are established prognostic factors, the interplay between acute metabolic derangement and chronic comorbidity burden remains poorly characterized. This study evaluated the prognostic value of the lactate/albumin Ratio (LAR) and the Charlson Comorbidity Index (CCI). Secondary endpoints included identifying independent mortality predictors and establishing the lethal area 50 percent (LA50) thresholds.

METHODS

A retrospective study at a National Burn Center (location blinded) included all patients aged > 65 years with burns > 10% TBSA (2012-2025). The LAR assessed the coupling of tissue hypoxia and nutritional status. Chronic disease burden was quantified using the weighted CCI. Multivariate logistic regression identified risk factors for in-hospital mortality.

RESULTS

Among 243 patients (mean age 75.8 years, TBSA 26.9%), mortality was 35.0%. In the complete-case analysis for biomarkers (n = 178), LAR discrimination was strong (AUC=0.84), comparable to lactate alone (mmol/L) (AUC=0.81, p = 0.09), but significantly superior to albumin (g/dL) (AUC=0.74, p = 0.014). A cut-off of LAR > 1.0 was identified as a critical threshold for mortality. In multivariate analysis, while binary comorbidities showed no significance, the CCI emerged as a robust independent predictor (OR 1.71, p < 0.001). Other independent predictors included TBSA, inhalation injury, and the LAR (OR 2.15, p = 0.006). The LA50 threshold was established at 34% TBSA.

CONCLUSION

Mortality in older adults can be interpreted through a conceptual "double hit" model: acute metabolic shock (LAR) and chronic comorbidities (CCI). The LAR offers comparable predictive value to isolated markers while integrating nutritional status, suggesting an exploratory and cohort-specific "LAR Unity Threshold" for risk stratification.