Association of Brain Atrophy and Masseter Sarcopenia With 1-Year Mortality in Older Trauma Patients

Abstract

Importance: Older adults are disproportionately affected by trauma and accounted for 47% of trauma fatalities in 2016. In many populations and disease processes, described risk factors for poor clinical outcomes include sarcopenia and brain atrophy, but these remain to be fully characterized in older trauma patients. Sarcopenia and brain atrophy may be opportunistically evaluated via head computed tomography, which is often performed during the initial trauma evaluation.

Objective: To investigate the association of masseter sarcopenia and brain atrophy with 1-year mortality among trauma patients older than 65 years by using opportunistic computed tomography imaging.

Design, setting, and participants: This retrospective cohort study was conducted in a level 1 trauma center from January 1, 2011, to December 31, 2014, with a 1-year follow-up to assess mortality. Washington state residents 65 years or older who were admitted to the trauma intensive care unit with a head Abbreviated Injury Scale score of less than 3 were eligible. Patients with incomplete data and death within 1 day of admission were excluded. Data analysis was completed from June 2017 to October 2018.

Exposures: Masseter muscle cross-sectional area and brain atrophy index were measured using a standard clinical Picture Archiving and Communication System application to assess for sarcopenia and brain atrophy, respectively.

Main outcomes and measures: Primary outcome was 1-year mortality. Secondary outcomes were discharge disposition and 30-day mortality.

Results: The study cohort included 327 patients; 72 (22.0%) had sarcopenia only, 71 (21.7%) had brain atrophy only, 92 (28.1%) had both, and 92 (28.1%) had neither. The mean (SD) age was 77.8 (8.6) years, and 159 patients (48.6%) were women. After adjustment for age, comorbidity, complications, and injury characteristics, masseter sarcopenia and brain atrophy were both independently and cumulatively associated with mortality (masseter muscle cross-sectional area per SD less than the mean: hazard ratio, 2.0 [95% CI, 1.2-3.1]; P = .005; brain atrophy index per SD greater than the mean: hazard ratio, 2.0 [95% CI, 1.1-3.5]; P = .02).

Conclusions and relevance: Masseter muscle sarcopenia and brain atrophy were independently and cumulatively associated with 1-year mortality in older trauma patients after adjustment for other clinical factors. These radiologic indicators are easily measured opportunistically through standard imaging software. The results can potentially guide conversations regarding prognosis and interventions with patients and their families.

Figure 1.. Example Masseter and Brain Atrophy Index Measurements

A, Measurement of masseter muscle cross-sectional area in the axial plan, 2 cm below the inferior edge of the zygomatic arch. The masseter is highlighted in brown. B, Measurements taken to calculate brain atrophy index (intercaudate distance divided by interskull distance in the axial plane at the level of the fornix). The 2 medial-facing arrows show the caudate (intercaudate distance). The longer, double-arrow line shows the interskull distance, which is measured at the same coronal plane as the intercaudate distance.

Figure 2.. Kaplan-Meier Survival Estimates

Patients were divided into 4 groups based on the median masseter cross-sectional area and brain atrophy index. Overall log-rank outcome was χ²₃ = 10.86 (P = .01). Pairwise comparison log-rank P values were adjusted with Bonferroni correction (patients with both conditions vs patients with neither condition, χ²₁ = 10.45; P = .007; patients with brain atrophy only vs patients with neither condition, χ²₁ = 2.39; P = .72; patients with masseter sarcopenia only vs patients with neither condition, χ²₁ = 2.45; P = .71; patients with brain atrophy vs patients with masseter sarcopenia, χ²₁ = 0.00; P > .99; patients with both conditions vs patients with brain atrophy only, χ²₁ = 2.52; P = .68; patients with both conditions vs patients with masseter sarcopenia only, χ²₁ = 2.27; P = .79).