Incidence and Clinical Characteristics of Respiratory Sarcopenia in Community-Dwelling Older Adults: A Cross-Sectional Study

Purpose: This study aimed to determine the prevalence, characteristics, and associated factors of respiratory sarcopenia in community-dwelling older adults. Methods: This cross-sectional study included 369 community-dwelling older adults aged 65 years and above, living in Koto-ku, Tokyo, Japan. Measurements included body composition, physical function (grip strength, walking speed, and 5 chair-stand, 5CS, test), physical activity (the International Physical Activity Questionnaire-Short Form), respiratory muscle strength (%Maximal Inspiratory Pressure, %MIP, and %Maximal Expiratory Pressure, %MEP), oral function (oral diadochokinesis, ODK; tongue pressure), cognitive function (Montreal Cognitive Assessment-Japanese), and health-related quality of life (the MOS 8-Item Short-Form Health Survey). Participants were classified into three mutually exclusive groups based on respiratory muscle strength and limb skeletal muscle mass. The Probable respiratory sarcopenia group (Probable group) included individuals with both reduced respiratory muscle strength (defined as both %MIP and %MEP values below 80%) and low limb skeletal muscle mass (defined as <7 kg/m² in men and <5.7 kg/m² in women, based on the Asian Working Group of Sarcopenia 2019). The Possible respiratory sarcopenia group (Possible group) included participants with reduced respiratory muscle strength alone but normal skeletal muscle mass. The Robust group comprised those with neither respiratory muscle weakness nor low skeletal muscle mass. The prevalence of each group was calculated separately. For further analysis, the Probable and Possible groups were combined into a single respiratory sarcopenia group, and the Robust group was used as the control. A t-test, Mann-Whitney U test, and chi-square test were used to compare the characteristics of each group. Logistic regression analysis was then performed to identify factors associated with the presence of respiratory sarcopenia. Results: The prevalence of Probable respiratory sarcopenia was 3.3%, and that of Possible respiratory sarcopenia was 33.3%. Compared with the Robust group, the respiratory sarcopenia group exhibited significantly poorer physical function, including grip strength, gait speed, 5CS performance, physical activity, and oral function. Additionally, cognitive function was significantly lower in the respiratory sarcopenia group. Significant factors associated with respiratory sarcopenia included grip strength, 5CS, moderate physical activity, tongue pressure, and fat-free mass. Conclusion: The prevalence of Probable respiratory sarcopenia and Possible respiratory sarcopenia among community-dwelling older adults was 3.3% and 33.3%, respectively. Respiratory sarcopenia was characterized by significantly lower physical function (grip strength, gait speed, and 5CS), physical activity, oral function (ODK and tongue pressure), and cognitive function. Furthermore, grip strength, 5CS score, moderate physical activity, and tongue pressure were identified as significant factors associated with respiratory sarcopenia, suggesting that it requires a comprehensive evaluation including physical function, physical activity, oral function, and cognitive function.