Muscularity of older trauma patients at intensive care unit admission, association with functional outcomes, and relationship with frailty: A retrospective observational study

Background: Older individuals are at an increased risk of delayed recovery following a traumatic injury. Measurement of muscularity and frailty at hospital admission may aid with prognostication and risk stratification. Objective: This study aimed to describe muscularity at intensive care unit (ICU) admission in patients admitted following trauma and assess the relationship between muscularity and clinical, long-term functional outcomes and frailty at ICU admission. Methods: This retrospective study utilised data from a prospective observational study investigating frailty in patients aged ≥50 years, admitted to the ICU following trauma. Patients were eligible if they had a Computed Tomography (CT) scan including the third lumbar vertebra at ICU admission. Specialist software was used to quantify CT-derived skeletal muscle cross-sectional area. Muscularity status was classified as normal or low using published sex-specific cut-points. Demographic data, frailty, clinical, and long-term functional outcomes (Glasgow Outcome Scale-Extended and EQ-5DL-5L Visual analogue scale and utility score) were extracted from the original study. Results: One hundred patients were screened; 71 patients had a CT scan on admission with 66 scans suitable for muscle assessment. Patients with low muscularity (n = 25, 38%) were older and had a higher Acute Physiology and Chronic Health Evaluation II score and lower body mass index than patients with normal muscularity. Low muscularity was associated with frailty at admission (32% vs 5%, p = 0.005) but not with long term outcomes at 6 or 12 months. As a continuous variable, lower muscle cross-sectional area was associated with a poorer outcome on the Glasgow Outcome Scale-Extended at 6 months (mean [standard deviation]: 150 [43] and 180 [44], respectively; p = 0.014), no association was observed after adjustment for age p = 0.43). Conclusion: In a population of older adults hospitalised following trauma, low muscularity at ICU admission was prevalent. Low muscularity was associated with frailty but not long-term functional outcomes. Larger studies are warranted to better understand the relationship between muscularity and long-term functional outcomes.