Leg, trunk mass decline in COPD patients

Fat-free mass (FFM) significantly decreases among patients with chronic obstructive pulmonary disease (COPD) after 2 years of follow-up, a recent study has found. Such decline is more noticeable in the legs and trunk.

“Patients with COPD with higher baseline FFM index and occurrence of recent hospitalizations were identified as a subgroup presenting greater decline in total and legs FFM,” the researchers said. “Longitudinal changes in body composition are weakly associated with longitudinal changes in lung function, symptoms of dyspnoea, and health-related quality of life.”

This analysis included patients with COPD and non-COPD controls participating in the Individualized COPD Evaluation in relation to Ageing (ICE-Age) study, a single-centre, longitudinal, observational study. Participants were evaluated at baseline and at 2-year follow-up.

The researchers measured body composition using dual-energy X-ray absorptiometry (DEXA) scan, among other procedures, and assessed the number of exacerbations/hospitalizations in COPD patients 1 year before inclusion and during follow-up.

Of the 405 participants, 205 had COPD, 87 were smoking controls, and 113 were nonsmoking controls. COPD patients (mean, –1,173 g, 95 percent confidence interval [CI], –1,527 to –820) and smokers (mean, –486 g, 95 percent CI, –816 to –156) showed a significant decline in total FFM, while nonsmokers had stable body composition. [Respirology 2021;26:851-860]

The decline in FFM in COPD patients was more pronounced in legs (mean, –174 g, 95 percent CI, –361 to 14) and trunk (mean, –675 g, 95 percent CI, –944 to 406) rather than in arms (mean, 54 g, 95 percent CI, –19 to 126). Gender, number of previous hospitalizations, baseline values of FFM, and body mass index were predictive of changes in total and regional FFM in this cohort.

In earlier studies, no difference was observed in longitudinal changes of body composition between COPD patients and non-COPD controls. [Ann Nutr Metab 2013;63:239-247; Thorax 2011;66:961-969]

“We hypothesize that the difference between these findings is caused by differences in the population included (eg, older [patients] with obstructive lung disease) and methods of assessment of body composition (bio-electrical impedance analysis vs DEXA scan),” the researchers said.

The finding on arms FFM showing no changes despite presenting a significant decline in legs FFM after 2 years of follow-up was possibly due to higher intensity physical activity, which is reduced in this population, being closely associated with legs dysfunction, while most activities of daily living are done with arms. [Am J Respir Crit Care Med 2005;171:972-927]

“Previous studies have found that patients with COPD present relatively preserved characteristics in arms compared with legs regarding muscle strength and endurance, mechanical efficiency, oxidative capacity, and duration of daily arm activities, despite lower intensity and at cost of higher effort of trapezius compared with healthy control subjects,” the researchers noted. [Eur Respir J 2014;43:1631-1641; Eur Respir J 2000;15:92-97; Med Sci Sports Exerc 2005;37:2-9; Med Sci Sports Exerc 2002;34:1570-1576; Eur Respir J 2001;17:939-945]

As regards changes in trunk body composition, previous studies found that the decrease in trunk FFM presented specifically in patients with worse disease severity or emphysema. The present study did not find any lung function factor independently associated with the change in trunk FFM. [Am J Clin Nutr 2000;71:733-738; PLoS One 2017;12:e0180928]