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Muscle Loss May Predict Mortality Risk in Smokers

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Embargoed until May 21, 9:15 a.m. ET

 

FOR MORE INFORMATION, CONTACT:
Dacia Morris
dmorris@thoracic.org
ATS Office 212-315-8620 (until May 17)
Cell Phone 917-561-6545

 

Session: A14 COPD: Systems Biology and Comorbidity
Abstract Presentation Time: Sunday, May 21, 9:30 a.m. ET
Location: Walter E. Washington Convention Center, Room 202A (South Bldg., Level 2)

 

ATS 2017, WASHINGTON, DC─Smokers with diminished chest muscle may face a greater risk of death than those smokers with more chest muscle, whether they have chronic obstructive pulmonary disease (COPD) or not, according to new research presented at the ATS 2017 International Conference.

“Prior studies found that smoking resulted in muscle damage and loss of muscle, even in so- called healthy smokers,” said lead study author Alejandro A Diaz, MD, instructor in medicine at Harvard. “But whether that loss of muscle was associated with higher death rates was not known.”           

The researchers analyzed computed tomography (CT) scans from 6,971 smokers (average age 60); more than half (55 percent) had COPD. In addition to determining the extent of COPD, the scans were used to measure the chest, or pectoralis, and the muscles along the spine, or paravertebral, muscle areas (PMA and PVMA, respectively). Participants were followed for more than five years on average. During that time, 653 died.

The study found:

  • Smokers in the bottom quartile of PMA (but not PVMA) were 120 percent more likely to die than smokers in the top quartile.
  • The addition of PMA to a multivariable model to predict survival in participants with and without COPD resulted in accurately reclassifying the risk of death in 10.2 percent of all participants.
  • Although those with COPD were more likely to die, the association between low PMA and death was stronger for those smokers without COPD than those with the disease.

“This is an interesting finding,” Dr. Diaz said. “In smokers with COPD, it may be that other factors—for example, oxygen use because of respiratory failure—make the contribution of muscle loss less important.”

The authors adjusted for a range of factors that influence muscle health and mortality, including age, race, smoking history, disease severity and comorbidities.

Dr. Diaz noted that while muscle mass is not routinely measured in those with COPD or those who smoke, smokers who meet certain criteria are now recommended for CT lung cancer screening.

“Pectoralis mass is easily identified on chest CT scans,” he said. “Adding this information may help clinicians identify those at greatest risk of dying from smoking.”

Contact for Media: Alejandro A. Diaz, MD, MPH, adiaz6@partners.org

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Abstract 8674

Low Muscle Mass and Mortality in Smokers with and Without COPD

Authors: A.A. Diaz1, C.H. Martinez2, R. Harmouche1, T.P. Young3, M.-L.N. McDonald4, J. Ross1, R. San Jose Estepar1, M.K. Han5, R.P. Bowler6, B.J. Make7, E. Regan7, E.K. Silverman1, J.D. Crapo7, G. Kinney8, J. Hokanson8, G. Washko9; 1Brigham and Women's Hospital - Boston, MA/US, 2University of Michigan - Ann Arbor, MI/US, 3Brigham and Women Hospital - Boston, MA/US, 4Brigham and Women's Hospital/ Harvard Medical School - Boston, MA/US, 5University of Michigan Health System - Ann Arbor, MI/US, 6National Jewish Medical and Research Center - Denver, CO/US, 7National Jewish Health - Denver, CO/US, 8University of Colorado - Aurora, CO/US, 9Brigham and Women's Hospital, Harvard Medical School - Boston, MA/US; for the COPDGene investigators

Rationale: Loss of muscle mass is associated with increased mortality in COPD subjects. Smokers without COPD also manifest many of the same comorbid conditions as those with COPD.

Objectives: To test the hypothesis that reduced muscle mass is associated with increased mortality in smokers without COPD.

Methods: We measured both pectoralis and paravertebral erector spinae muscle area (PMA and PVMA, respectively) as well as emphysema on chest computed tomography (CT) scans from 6,971 smokers with and without COPD. The contribution of muscle mass to death risk prediction was assessed using Cox regression models, and C and net reclassification indices. PMA and PVMA were divided in quartiles with the highest used as referent.

Measurements and Main Results: At baseline, 55% of participants had COPD. During 5.4 years mean follow- up, 653 (9.4%) died. Overall, smokers in the lowest (vs. highest) quartile of PMA but not PVMA had a higher risk of death (hazard ratio [HR] 2.20, 95% Confidence interval 1.58–3.05; P<0.001) in adjusted models (Figure 1).

The risk differed between smokers with (HR 1.71, 1.09–2.67; P=0.02) and without COPD (HR 2.73, 1.58–4.73; P<0.001). The addition of PMA to multivariable models increased the discrimination of death modestly (C-index value increase, 0.01; P<0.001) and correctly reclassified the risk of death in (mean ± SE) 10.2% ± 1.7% of the participants (P<0.001).

Conclusions: Low muscle mass is associated with increased mortality in smokers with and without COPD. This simple measurement of muscle mass readily obtained from CT scans appears to improve mortality risk assessment.