Sarcopenia and possible respiratory sarcopenia in interstitial lung diseases: a cross-sectional study on prevalence and functional impairment

Abstract Background Patients with interstitial lung diseases (ILD) frequently experience impaired physical health and quality of life, often complicated by sarcopenia or respiratory sarcopenia. This study investigates the prevalence and characteristics of sarcopenia and respiratory sarcopenia in ILD patients, aiming to inform personalized management and rehabilitation strategies. Methods A cross-sectional observational study was conducted, involving baseline data collection and comprehensive assessments, including questionnaires, physical fitness tests, pulmonary function tests, and ultrasound examinations. Sarcopenia was diagnosed using the Asian Working Group for Sarcopenia 2019 criteria. Respiratory muscle weakness was defined as maximal inspiratory pressure (MIP) < 80% of the predicted value, and possible respiratory sarcopenia was identified as the coexistence of sarcopenia and respiratory muscle weakness. Participants were stratified for subgroup analysis. Results This study included 70 ILD patients (38 males, mean age 63.0 ± 12.1 years), with 50% having connective tissue disease-associated ILD (CTD-ILD) and 50% idiopathic interstitial pneumonia (IIP). Sarcopenia prevalence was 31.4% (22/70), decreased respiratory muscle strength 40.0% (28/70), and possible respiratory sarcopenia 18.6% (13/70). Subgroup analyses showed higher malnutrition rates across all groups, with significant declines in handgrip strength, knee extension strength, Short Physical Performance Battery score, 6-min walk distance, and respiratory muscle strength. Daily living activities and SF-36 scores also decreased, with more pronounced effects in patients with possible respiratory sarcopenia. Conclusion ILD patients with sarcopenia or possible respiratory sarcopenia exhibit significant declines in physical fitness, respiratory function, daily activities, and quality of life, with the most pronounced reductions in those with possible respiratory sarcopenia.