Pectoralis muscle area and mortality in smokers without airflow obstruction

Alejandro A Diaz,Carlos H Martinez,Elizabeth A Regan,George R Washko,Rola Harmouche,John E Hokanson,James Crapo,Edwin K Silverman,Aladin M Boriek,Gregory L Kinney,Raul San Jose Estepar,Merry-Lynn Mcdonald,Thomas P Young,James C Ross,Mei Lan Han,Russell Bowler,Barry Make

doi:10.1186/s12931-018-0771-6

Abstract

BackgroundLow muscle mass is associated with increased mortality in the general population but its prognostic value in at-risk smokers, those without expiratory airflow obstruction, is unknown. We aimed to test the hypothesis that reduced muscle mass is associated with increased mortality in at-risk smokers.MethodsMeasures of both pectoralis and paravertebral erector spinae muscle cross-sectional area (PMA and PVMA, respectively) as well as emphysema on chest computed tomography (CT) scans were performed in 3705 current and former at-risk smokers (≥10 pack-years) aged 45–80 years enrolled into the COPDGene Study between 2008 and 2013. Vital status was ascertained through death certificate. The association between low muscle mass and mortality was assessed using Cox regression analysis.ResultsDuring a median of 6.5 years of follow-up, 212 (5.7%) at-risk smokers died. At-risk smokers in the lowest (vs. highest) sex-specific quartile of PMA but not PVMA had 84% higher risk of death in adjusted models for demographics, smoking, dyspnea, comorbidities, exercise capacity, lung function, emphysema on CT, and coronary artery calcium content (hazard ratio [HR] 1.85 95% Confidence interval [1.14–3.00] P = 0.01). Results were consistent when the PMA index (PMA/height2) was used instead of quartiles. The association between PMA and death was modified by smoking status (P = 0.04). Current smokers had a significantly increased risk of death (lowest vs. highest PMA quartile, HR 2.25 [1.25–4.03] P = 0.007) while former smokers did not.ConclusionsLow muscle mass as measured on chest CT scans is associated with increased mortality in current smokers without airflow obstruction.Trial registrationNCT00608764

Highlights

Low muscle mass is associated with increased mortality in the general population but its prognostic value in at-risk smokers, those without expiratory airflow obstruction, is unknown
We examined the computed tomographic (CT) and clinical data obtained in the COPDGene Study [28]
The baseline characteristics of the cohort are provided by pectoralis muscle area (PMA) quartile in Table 1 and by paravertebral muscle area (PVMA) quartile (Additional file 1: Table S1)

Summary

Introduction

Low muscle mass is associated with increased mortality in the general population but its prognostic value in at-risk smokers, those without expiratory airflow obstruction, is unknown. A myriad of studies has demonstrated that the CT cross-sectional area of mid-thigh, pectoralis, and paravertebral erector spinae muscles are associated with fat-free mass, handgrip strength, exercise capacity, health status, and COPD severity [22,23,24,25]. These CT measures were predictive of mortality in subjects with established COPD [23, 24, 26]. CT allows measuring fat depots including subcutaneous adipose tissue and provides additional prognostic understanding of the body composition [27]

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