Supplementary Material for: Centrilobular Emphysema Is Associated with Pectoralis Muscle Reduction in Current Smokers without Airflow Limitation

<b><i>Background:</i></b> Physiological and prognostic associations of centrilobular emphysema (CLE) and paraseptal emphysema (PSE) in smokers with and without chronic obstructive pulmonary disease (COPD) have been increasingly recognized, but the associations with extrapulmonary abnormalities, such as muscle wasting, osteoporosis, and cardiovascular diseases, remain unestablished. <b><i>Objectives:</i></b> The aim of the study was to investigate whether CLE was associated with extrapulmonary abnormalities independent of concomitant PSE in smokers without airflow limitation. <b><i>Methods:</i></b> This retrospective study consecutively enrolled current smokers without airflow limitation who underwent lung cancer screening with computed tomography and spirometry. CLE and PSE were visually identified based on the Fleischner Society classification system. Cross-sectional areas of pectoralis muscles (PM) and adjacent subcutaneous adipose tissue (SAT), bone mineral density (BMD), and coronary artery calcification (CAC) were evaluated. <b><i>Results:</i></b> Of 310 current smokers without airflow limitation, 83 (26.8%) had CLE. The PSE prevalence was higher (67.5% vs. 23.3%), and PM area, SAT area, and BMD were lower in smokers with CLE than in those without (PM area (mean), 34.5 versus 38.6 cm²; SAT area (mean), 29.3 versus 36.8 cm²; BMD (mean), 158.3 versus 178.4 Hounsfield unit), while CAC presence did not differ. In multivariable models, CLE was associated with lower PM area but not with SAT area or BMD, after adjusting for PSE presence, demographics, and forced expiratory volume in 1 s. <b><i>Conclusions:</i></b> The observed association between CLE and lower PM area suggests that susceptibility to skeletal muscle loss could be high in smokers with CLE even without COPD.

**研究背景：** 目前学界已逐渐明确吸烟人群（无论是否合并慢性阻塞性肺疾病（COPD））中小叶中心型肺气肿（CLE）与小叶间隔旁型肺气肿（PSE）的生理学及预后关联，但二者与肌肉消耗、骨质疏松、心血管疾病等肺外异常的关联仍未明确。
**研究目的：** 本研究旨在探讨在无气流受限的吸烟人群中，CLE是否与肺外异常存在独立于伴随性PSE的关联。
**研究方法：** 本回顾性研究连续纳入了接受计算机断层扫描（computed tomography, CT）肺癌筛查与肺量测定（spirometry）的无气流受限当前吸烟者。依据弗莱施纳学会（Fleischner Society）分类标准，通过视觉识别法判定CLE与PSE。研究人员对胸大肌（PM）及邻近皮下脂肪组织（SAT）的横截面积、骨密度（BMD）以及冠状动脉钙化（CAC）进行了评估。
**研究结果：** 在310例无气流受限的当前吸烟者中，83例（26.8%）存在CLE。与无CLE的吸烟者相比，合并CLE者的PSE患病率更高（67.5% vs. 23.3%），胸大肌横截面积、皮下脂肪组织横截面积及骨密度均更低：胸大肌横截面积（均值）分别为34.5 cm²与38.6 cm²；皮下脂肪组织横截面积（均值）分别为29.3 cm²与36.8 cm²；骨密度（均值）分别为158.3与178.4亨斯菲尔德单位（Hounsfield unit, HU），但冠状动脉钙化的检出率无显著差异。多变量模型分析显示，在校正PSE存在情况、人口学特征及1秒用力呼气容积（forced expiratory volume in 1 s）后，CLE仅与更低的胸大肌横截面积相关，而与皮下脂肪组织横截面积或骨密度无显著关联。
**研究结论：** 本研究观察到CLE与更低的胸大肌横截面积存在关联，这提示即使未合并COPD，合并CLE的吸烟者发生骨骼肌丢失的易感性也可能更高。