Longitudinal changes in appendicular skeletal muscle mass among asthma and COPD subjects: The Rotterdam Study

Background: Low lean mass is a highly prevalent condition in the elderly population. In patients with COPD, lean mass declines further with advancing age. In asthmatic patients, the age-dependent lean mass loss is less well-studied. We aimed at determining the degree of longitudinal change in appendicular skeletal muscle mass observed in elderly individuals with COPD and asthma. Methods: All 492 prevalent COPD cases, 186 prevalent asthma cases and 2556 participants without COPD or asthma, with more than two dual-energy X-ray absorptiometry scans (11.6 years of follow-up) were included. A linear mixed-effects model was fitted for appendicular lean mass, with natural cubic splines for age and their interactions with sex and chronic respiratory diseases, adjusted for smoking status, corticosteroids use and body mass index (BMI). Results: Asthma participants had a lower trajectory of appendicular lean mass at younger ages than those without either respiratory disease, irrespective of sex, smoking status, oral corticosteroids use and BMI (β=-1.14, 95% CI -1.84, -0.44, p=0.033). Trajectories of appendicular lean mass in participants with COPD were linear for both sexes while those of participants with asthma were curved (Figure 1). Conclusion: Our study confirms the longitudinal linear age-dependent muscle loss in COPD participants and adds that asthmatic subjects had a significantly non-linear loss of appendicular lean mass. Figure 1: Longitudinal changes in appendicular lean mass according to sex and chronic respiratory diseases. Red lines show the change in the coefficient (β) of appendicular lean mass over years of age with 95% CIs which are indicated by black dot lines.