Body Composition in Severe Refractory Asthma: Comparison with COPD Patients and Healthy Smokers

BACKGROUND Body composition is an important parameter for patients with chronic obstructive pulmonary disease (COPD) whereas the association between asthma and obesity is not fully understood. The impact of severe refractory asthma (SRA) on fat free mass (FFM) has not been investigated. METHODOLOGY AND PRINCIPAL FINDINGS 213 subjects (70 healthy smokers, 71 COPD patients and 72 asthma patients) without significant comorbidities were included in the study. In all patients, body composition assessment (using bioelectrical impendance analysis, skinfold and anthropometric measurements) and spirometry were performed. Differences in fat free mass index (FFMI) between groups were assessed and determinants of FFMI in asthma were evaluated. Patients with SRA had lower values of FFMI compared to patients with mild-to-moderate asthma [18.0(17.3-18.3)-19.5(18.4-21.5), p<0.001], despite the fact that they were more obese. The levels of FFMI in SRA were lower than those of GOLD stage I-III COPD and comparable to those of stage IV COPD patients [18.0(17.3-18.3)-18.8(17.8-20.1), p = ns]. These differences were present even after proper adjustments for sex, age, smoking status, daily dose of inhaled corticosteroids (ICS) and daily use of oral corticosteroids (OCS). In multivariate analysis, independent predictors of FFMI in asthmatic patients were age, use of OCS and the presence of SRA, but not smoking, sex or cumulative dose of ICS used. CONCLUSIONS AND SIGNIFICANCE SRA is related to the presence of low FFMI that is comparable to that of GOLD stage IV COPD. The impact of this observation on asthma mechanisms and outcomes should be further investigated in large prospective studies.