Pulmonary, Allergy, and Critical Care Medicine, University of Pittsburgh Medical Center, Pittsburgh, Pennsylvania, USA.
University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA.
Thorax. 2023 Apr;78(4):394-401. doi: 10.1136/thoraxjnl-2021-217710. Epub 2021 Dec 1.
Muscle loss is an important extrapulmonary manifestation of COPD. Dual energy X-ray absorptiometry (DXA) is the method of choice for body composition measurement but is not widely used for muscle mass evaluation. The pectoralis muscle area (PMA) is quantifiable by CT and predicts cross-sectional COPD-related morbidity. There are no studies that compare PMA with DXA measures or that evaluate longitudinal relationships between PMA and lung disease progression.
Participants from our longitudinal tobacco-exposed cohort had baseline and 6-year chest CT (n=259) and DXA (n=164) data. Emphysema was quantified by CT density histogram parenchymal scoring using the 15th percentile technique. Fat-free mass index (FFMI) and appendicular skeletal mass index (ASMI) were calculated from DXA measurements. Linear regression model relationships were reported using standardised coefficient (β) with 95% CI.
PMA was more strongly associated with DXA measures than with body mass index (BMI) in both cross-sectional (FFMI: β=0.76 (95% CI 0.65 to 0.86), p<0.001; ASMI: β=0.76 (95% CI 0.66 to 0.86), p<0.001; BMI: β=0.36 (95% CI 0.25 to 0.47), p<0.001) and longitudinal (ΔFFMI: β=0.43 (95% CI 0.28 to 0.57), p<0.001; ΔASMI: β=0.42 (95% CI 0.27 to 0.57), p<0.001; ΔBMI: β=0.34 (95% CI 0.22 to 0.46), p<0.001) models. Six-year change in PMA was associated with 6-year change in emphysema (β=0.39 (95% CI 0.23 to 0.56), p<0.001) but not with 6-year change in airflow obstruction.
PMA is an accessible measure of muscle mass and may serve as a useful clinical surrogate for assessing skeletal muscle loss in smokers. Decreased PMA correlated with emphysema progression but not lung function decline, suggesting a difference in the pathophysiology driving emphysema, airflow obstruction and comorbidity risk.
肌肉减少是 COPD 的一种重要的肺外表现。双能 X 射线吸收法（DXA）是用于身体成分测量的首选方法，但不适用于肌肉质量评估。通过 CT 可量化胸肌面积（PMA），并可预测 COPD 相关发病率的横断面。目前尚无研究比较 PMA 与 DXA 测量值，或评估 PMA 与肺部疾病进展之间的纵向关系。
我们的纵向吸烟队列的参与者具有基线和 6 年胸部 CT（n=259）和 DXA（n=164）数据。使用 15%密度直方图实质评分技术通过 CT 量化肺气肿。从 DXA 测量值中计算出瘦体重指数（FFMI）和四肢骨骼质量指数（ASMI）。使用标准化系数（β）和 95%置信区间（CI）报告线性回归模型关系。
在横断面（FFMI：β=0.76（95%CI 0.65 至 0.86），p<0.001；ASMI：β=0.76（95%CI 0.66 至 0.86），p<0.001；BMI：β=0.36（95%CI 0.25 至 0.47），p<0.001）和纵向（ΔFFMI：β=0.43（95%CI 0.28 至 0.57），p<0.001；ΔASMI：β=0.42（95%CI 0.27 至 0.57），p<0.001；ΔBMI：β=0.34（95%CI 0.22 至 0.46），p<0.001）模型中，PMA 与 DXA 测量值的相关性均强于 BMI。6 年 PMA 变化与 6 年肺气肿变化相关（β=0.39（95%CI 0.23 至 0.56），p<0.001），但与气流阻塞的 6 年变化无关。
PMA 是肌肉质量的一种可获得的测量方法，可能是评估吸烟者骨骼肌损失的有用临床替代指标。PMA 降低与肺气肿进展相关，但与肺功能下降无关，这表明驱动肺气肿、气流阻塞和合并症风险的病理生理学存在差异。
