Characteristics of Probable Respiratory Sarcopenia Based on the Definitions of Four Professional Organizations—The Otassha Study

ABSTRACT Background The new position paper on the definition and diagnosis of respiratory sarcopenia defines respiratory sarcopenia as a decrease in respiratory muscle strength and mass. It recommends using a decrease in limb muscle mass as a substitute for respiratory muscle mass, which is difficult to measure, and recommends that such cases be diagnosed as “probable respiratory sarcopenia” with appropriate interventions. This study aimed to determine the physical characteristics of older adults with probable respiratory sarcopenia based on current criteria. Methods A total of 496 community‐dwelling older adults were enrolled in this study, completing an evaluation of respiratory and physical function in 2023 as part of a comprehensive health check‐up program called the Otassha study. The respiratory and physical functions, comorbidities, instrumental activities of daily living, and lifestyles of the participants were measured. “Probable respiratory sarcopenia” was compared to non‐respiratory sarcopenia with respect to respiratory and physical functions. Probable respiratory sarcopenia was determined using low maximal mouth pressure (< 80% of predicted value) and low appendicular skeletal muscle mass (ASM)/height 2 (7.0 kg/m 2 for men and 5.7 kg/m 2 for women). The association between probable respiratory sarcopenia (as the independent variable) and physical and peak expiratory flow rate (PEFR) (as dependent variables), adjusted for covariates, was evaluated using a multivariate linear regression model. A 2:1 matched pair of individuals with non‐respiratory sarcopenia and probable respiratory sarcopenia was compared using propensity score matching (PSM) to account for confounders. Results The prevalence of probable respiratory sarcopenia was 33 out of 185 (17.8%) in men and 65 out of 311 (20.9%) in women. Grip strength, knee extension strength, and PEFR were significantly associated with probable respiratory sarcopenia ( p = 0.001 to p < 0.01). In the PSM data set, compared to non‐respiratory sarcopenia, those with probable respiratory sarcopenia showed significantly lower values for respiratory function, grip strength, and knee extension strength, cognitive function, as well as a higher prevalence of whole‐body sarcopenia ( p = 0.028 to p < 0.001). Conclusion Probable sarcopenia is characterized by low limb muscle strength and impaired respiratory and physical function. Understanding this aspect of suspected respiratory sarcopenia can aid in early detection and treatment management, leading to improved future health outcomes.