Muscle loss may predict mortality risk in smokers, study suggests.
The Centers for Disease Control and Prevention (CDC) report that cigarette smoking is the number one cause of preventable disease and death in the United States.
Smoking is responsible for more than 480,000 yearly deaths. Despite this, around 36.5 million U.S. individuals continue to smoke, and another 16 million live with a disease related to smoking.
A new study set out to examine the hypothesis that a lower muscle mass correlates with higher mortality in smokers who do not have chronic obstructive pulmonary disease (COPD). The findings were presented at the American Thoracic Society 2017 conference.
The study's lead author, Dr. Alejandro A. Diaz, instructor in medicine at Harvard University in Cambridge, MA, explains the motivation for the research, saying, "Prior studies found that smoking resulted in muscle damage and loss of muscle, even in so- called healthy smokers. But whether that loss of muscle was associated with higher death rates was not known."
Studying the link between chest muscles, smoking, and mortality
Regardless of whether the smokers have COPD or not, smokers who have less chest muscle may be likelier to die prematurely, suggests the study.
Diaz and team examined computed tomography (CT) scans from almost 7,000 smokers, who were aged 60 years on average. Over half (55 percent) of the participants had COPD.
The researchers also used the scans to measure the chest, or pectoralis muscle area (PMA), as well as the spine, or paravertebral muscle areas (PVMA).
The participants were clinically followed for an average period of 5 years. During the follow-up period, 653 patients died.
Diaz and team adjusted for a variety of risk factors that may impact the health of the muscles and the risk of mortality. These included race, age, smoking habits, and comorbidities. Researchers also considered the severity of COPD.
Low muscle mass linked to mortality in smokers with and without COPD
Participants were divided into quartiles, or fourths, according to their PMA and PVMA muscle mass.
The research revealed that smokers in the lowest quartile of PMA - but not PVMA - had a 120 percent higher chance of dying prematurely, compared with smokers in the highest quartile.
Additionally, by adding the PMA to the calculations, researchers were able to predict survival and "correctly reclassify" the risk of death in 10.2 percent of all COPD and COPD-free patients.
Finally, the correlation between low PMA and death risk was stronger for those without COPD than their counterparts with the disease. However, COPD patients were overall more likely to die.
The study's lead author comments on the findings, saying, "This is an interesting finding. 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."
"Pectoralis mass is easily identified on chest CT scans. Adding this information may help clinicians identify those at greatest risk of dying from smoking," Diaz says.
The authors conclude that:
"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."