Association of respiratory function with sarcopenia in older outpatients: cross-sectional analysis of baseline data from the JUSTICE-TOKYO prospective cohort study

Purpose Sarcopenia, characterized by the loss of skeletal muscle mass and function, can affect respiratory muscles and contribute to impaired pulmonary function. However, evidence on the association between sarcopenia and respiratory function in older adults remains limited. This study examined the relationship between sarcopenia and respiratory function in outpatients at a geriatric specialty hospital. Methods Baseline data from 810 outpatients aged 65 years or older enrolled in the JUSTICE-TOKYO study were analyzed. Patients with respiratory diseases such as asthma, chronic obstructive pulmonary disease, or interstitial lung disease were excluded. Sarcopenia was diagnosed using the 2019 Asian Working Group for Sarcopenia criteria. Pulmonary function measures included percent predicted vital capacity (%VC), percent predicted forced expiratory volume in one second (%FEV ₁ ), FEV ₁ /FVC ratio, and peak expiratory flow rate (PEFR). Receiver operating characteristic curve analyses were performed for %VC and PEFR to assess their diagnostic performance for sarcopenia. Results Sarcopenia was identified in 170 patients (21%; 102 men, 68 women). Patients with sarcopenia had a higher prevalence of myocardial infarction, heart failure, and malignancy. Receiver operating characteristic curve analyses showed that %VC had an optimal cutoff of 94.2%, with a sensitivity of 0.71, specificity of 0.63, and area under the curve of 0.66. The diagnostic performance of %VC was comparable to that of PEFR (area under the curve: 0.70 in men, 0.69 in women). Conclusion Respiratory function, particularly %VC, is significantly associated with sarcopenia in older outpatients. %VC may serve as a practical, standardized screening tool with diagnostic accuracy comparable to PEFR.