Frequency and clinical impact of low muscle mass in patients with asthma referred for pulmonary rehabilitation

Abstract

<b>Background:</b> one of the most prominent extra-pulmonary manifestations in patients with respiratory disease are body composition abnormalities. However, the frequency and functional consequences of low muscle mass in patients with asthma is largely unknown. <b>Aims:</b> to assess the frequency of low appendicular skeletal muscle mass index (ASMI) according to fixed and age-sex-body-mass index (BMI) specific cut-offs, and its functional consequences. <b>Methods:</b> a retrospective&nbsp;observational study was conducted in 673 patients with asthma referred for pulmonary rehabilitation (PR). Body composition, pulmonary and quadriceps muscle function, exercise capacity, and quality of life were assessed. The proportion of patients with low ASMI was compared among BMI categories and clinical outcomes between patients with normal&nbsp;vs low ASMI within each BMI category were compared. <b>Results:</b> the frequency of patients classified as low ASMI was 16% (fixed cut-offs) and 19% (age-sex-BMI-specific cut-offs; p&lt;0.05).&nbsp;In patients with normal weight, those with low ASMI were younger and had worse pulmonary function, exercise capacity and quadriceps muscle function than those with normal ASMI (all p&lt;0.05). Overweight patients with low ASMI presented poorer pulmonary function and quadriceps muscle function (both strength and total work capacity).&nbsp;In obese class I patients, those with low ASMI showed lower quadriceps strength and maximal oxygen uptake. <b>Conclusions:</b> one in five asthma patients referred for PR presented low muscle mass when age-sex-BMI-specific ASMI cut-offs were applied. Furthermore, lower muscle mass was associated with worse functional outcomes, in particular in the patients with normal weight.