CT-Derived Pectoralis Muscle Measurements and All-Cause Mortality in COPD

Background/Objectives: Skeletal muscle depletion is an important extrapulmonary manifestation of chronic obstructive pulmonary disease (COPD) and is associated with adverse clinical outcomes. Chest computed tomography (CT), which is frequently performed in patients with COPD, provides an opportunity for opportunistic assessment of thoracic muscle mass. However, the prognostic relevance of CT-derived pectoralis muscle measurements for long-term survival in COPD remains incompletely defined. This study aimed to evaluate the association between CT-derived pectoralis muscle measurements and all-cause mortality in patients with COPD and to compare the prognostic relevance of absolute muscle area and a height-adjusted index. Methods: In this retrospective cohort study, 245 patients with COPD who underwent chest CT were included. Pectoralis muscle area (PMA) was measured on a single axial image at the level of the fourth thoracic vertebra using a semi-automated segmentation method, and the pectoralis muscle index (PMI) was calculated by normalizing PMA to height squared. The primary endpoint was all-cause mortality. Multivariable Cox proportional hazards regression analyses were performed to assess the associations between muscle measurements and mortality, adjusting for age, sex, and selected clinical covariates. Hazard ratios (HRs) were expressed per 100-unit increase in PMA (mm²) and PMI. Results: During a mean follow-up of 5.31 ± 3.93 years, 178 deaths (72.7%) occurred. In multivariable analyses, higher PMA was significantly associated with a lower risk of all-cause mortality (HR per 100 mm² increase, 0.951; 95% confidence interval [CI], 0.933-0.969; p < 0.001). Similarly, higher PMI was significantly associated with lower mortality (HR per 100-unit increase in PMI, 0.879; 95% CI, 0.834-0.925; p < 0.001). In sex-stratified analyses, these associations remained significant in men but not in women. Conclusions: CT-derived pectoralis muscle measurements were significantly associated with all-cause mortality in patients with COPD. Both absolute muscle area and height-adjusted indices demonstrated consistent prognostic value. Opportunistic assessment of thoracic muscle on routine chest CT may provide a useful imaging biomarker for risk stratification in COPD.