# Subcutaneous Adipose Tissue Radiation Attenuation Is Associated With Increased 1‐Year Mortality in Polytrauma Patients

## TL;DR

This study shows that the radiation attenuation of subcutaneous fat in CT scans of trauma patients is linked to higher mortality within one year.

## Contribution

The novel finding is that subcutaneous adipose tissue radiation attenuation is a significant predictor of 1-year mortality in polytrauma patients.

## Key findings

- Subcutaneous adipose tissue radiation attenuation (SATRA) is significantly associated with increased 1-year mortality.
- Age and Injury Severity Score (ISS) remain significant predictors of 1-year mortality in polytrauma patients.
- Incorporating body composition analysis from CT scans may improve risk stratification for mortality.

## Abstract

Polytrauma patients with an Injury Severity Score (ISS) ≥ 16 have a high mortality rate. Early identification of patients at risk of mortality is key. Different risk stratification models are available; however, body composition on third lumbar computed tomography (L3 CT) is not routinely used. The aim of this study is to determine the effect of CT body composition on 1‐year mortality in adult polytrauma patients.

Body composition analysis (L3 CT) was performed on 593 adult polytrauma patients. The associations with 1‐year mortality were assessed using uni‐ and multivariable logistic regression analysis. As a sensitivity analysis, 1‐year mortality was analysed using Kaplan–Meier survival curves, log‐rank tests and Cox regression.

The study population was predominantly male (69.5%), with a mean age of 55 (±20) years and an average BMI of 25.34 kg/m2 (±4.07). Comorbidities were present in 327 (55.4%) patients, with an average Charlson Comorbidity Index (CCI) of 2.07 points (±2.1). The mean ISS score was 27.59 (±11.06); 323 (54.5%) patients had an ISS ≥ 25 points. Age, CCI, ISS, skeletal muscle index and skeletal muscle radiation attenuation (OR 1.053, 5.713, 3.711, 0. 563 and 0.533, respectively; p < 0.001), subcutaneous adipose tissue radiation attenuation (SATRA OR 1.253, p = 0.028) and visceral adipose tissue index (OR 1.242, p = 0.038) were significantly associated with 1‐year mortality. In multivariable logistic regression, age, ISS and SATRA remained statistically significantly associated with 1‐year mortality (OR 1.062, p < 0.001; OR 4.761, p < 0.001; OR 1.396, p = 0.009).

This study demonstrated that subcutaneous adipose tissue radiation attenuation on emergency trauma CT scans is significantly associated with 1‐year mortality in adult polytrauma patients. Additionally, we found a significant effect of age and ISS on 1‐year mortality. Incorporating body composition analysis could lead to a better selection of patients at risk for 1‐year mortality and aid in treatment decision‐making.