Pectoralis muscle area predicts in-hospital mortality in older COPD patients with pneumonia

BACKGROUND: Early prognostication in older adults with chronic obstructive pulmonary disease (COPD) hospitalized for pneumonia remains difficult, as traditional severity scores often fail to capture baseline physiological reserve. Thoracic muscle morphometry, derived from routine chest computed tomography (CT), has emerged as a feasible structural biomarker of frailty. This study investigated the independent prognostic value of pectoralis muscle area (PMA) for in-hospital mortality in this high-risk population.METHODS: In this single-center retrospective cohort (January 2019 - February 2020), 119 COPD patients aged ≥65 years admitted with pneumonia were included. Patients with active malignancy were excluded. Composite PMA was quantified at the aortic arch level from diagnostic-quality admission chest CTs. The primary outcome was in-hospital mortality. Cox proportional hazards models adjusted for Acute Physiology and Chronic Health Evaluation II (APACHE II) and clinical covariates were used to assess independent associations. Discriminatory performance was examined using receiver operating characteristic (ROC) analysis, and the functional form of the PMA-in-hospital mortality relationship was explored using restricted cubic splines.RESULTS: The overall in-hospital mortality rate was 40.3% (N.=48). PMA was significantly lower in non-survivors than in survivors (16.7 vs. 22.8 cm2, P<0.001). In multivariable analysis, PMA remained an independent predictor of mortality (hazard ratio HR 0.93 per 1-cm2 increase, 95% confidence interval CI 0.88-0.99; P=0.017; representing a 20-52% risk reduction per 3-10 cm2 increase), alongside APACHE II and organ support requirements. Notably, restricted cubic spline modeling revealed a linear inverse relationship between PMA and mortality risk, with no threshold effect. ROC analysis identified a PMA cutoff of ≤21.24 cm2 (area under the curve AUC = 0.71) for descriptive discrimination of mortality risk. Kaplan-Meier curves were generated for illustrative purposes.CONCLUSIONS: Pectoralis muscle area derived from routine admission chest CT serves as a supplementary and independent predictor of in-hospital mortality in older COPD patients with pneumonia. Beyond traditional severity scores, PMA functions as an objective marker of structural physiological reserve, potentially assisting in the identification of high-risk patients who may benefit from intensified monitoring and comprehensive supportive care.