This report was written by the Japanese Society of Dysphagia Rehabilitation, the Japanese Association of Rehabilitation Nutrition, the Japanese Association on Sarcopenia and Frailty, and the Society of Swallowing and Dysphagia of Japan to consolidate the currently available evidence on the topics of sarcopenia and dysphagia. Histologically, the swallowing muscles are of different embryological origin from somatic muscles, and receive constant input stimulation from the respiratory center. Although the swallowing muscles are striated, their characteristics are different from those of skeletal muscles. The swallowing muscles are inevitably affected by malnutrition and disuse; accumulating evidence is available regarding the influence of malnutrition on the swallowing muscles. Sarcopenic dysphagia is defined as dysphagia caused by sarcopenia of the whole body and swallowing‐related muscles. When sarcopenia does not exist in the entire body, the term “sarcopenic dysphagia” should not be used. Additionally, sarcopenia due to neuromuscular diseases should be excluded; however, aging and secondary sarcopenia after inactivity, malnutrition and disease (wasting disorder and cachexia) are included in sarcopenic dysphagia. The treatment of dysphagia due to sarcopenia requires both dysphagia rehabilitation, such as resistance training of the swallowing muscles and nutritional intervention. However, the fundamental issue of how dysphagia caused by sarcopenia of the swallowing muscles should be diagnosed remains unresolved. Furthermore, whether dysphagia can be caused by primary sarcopenia should be clarified. Additionally, more discussion is required on issues such as the relationship between dysphagia and secondary sarcopenia, as well as the diagnostic criteria and means for diagnosing dysphagia caused by sarcopenia. Geriatr Gerontol Int 2019; 19: 91–97.

The aim of this study was to investigate the effects of a leucine-enriched amino acid supplement on muscle mass, muscle strength, and physical function in post-stroke patients with sarcopenia. We conducted an eight-wk, two-parallel group intervention, randomized controlled, blinded outcome assessment among 44 post-stroke older patients with sarcopenia. Sarcopenia was defined as a loss of skeletal muscle mass and decreased muscle strength according to the Asian Working Group for Sarcopenia criteria. The intervention group (n = 21) received a leucine-enriched amino acid supplement; the control group (n = 23) did not. Both groups performed low-intensity resistance training in addition to a post-stroke rehabilitation program. A primary outcome of physical function by using the motor domain of Functional Independence Measure (FIM), and secondary outcomes of appendicular muscle mass (skeletal muscle mass index [SMI]) measured via bioelectrical impedance analysis and muscle strength as handgrip strength were measured at baseline and at the end of the intervention. The FIM score increased significantly in both groups over time (P < 0.01), with significantly greater improvement in the intervention group than in the control group (P < 0.045). Handgrip strength also increased significantly over time (P <0.05), with significantly greater improvement in the intervention group (P < 0.01). The SMI increased significantly in the intervention group but not in the control group over time, with significantly greater improvement in the intervention group (median estimated difference, 0.50 kg/m2; 95% confidence interval, 0.01-2.11). We demonstrated that an eight-wk intervention consisting of a leucine-enriched amino acid supplementation and low-intensity resistance training increased muscle mass, strength, and physical function in post-stroke patients with sarcopenia.

We defined respiratory sarcopenia as a coexistence of respiratory muscle weakness and decreased respiratory muscle mass. Although respiratory muscle function is indispensable for life support, its evaluation has not been included in the regular assessment of respiratory function or adequately evaluated in clinical practice. Considering this situation, we prepared a position paper outlining basic knowledge, diagnostic and assessment methods, mechanisms, involvement in respiratory diseases, intervention and treatment methods, and future perspectives on respiratory sarcopenia, and summarized the current consensus on respiratory sarcopenia. Respiratory sarcopenia is diagnosed when respiratory muscle weakness and decreased respiratory muscle mass are observed. If respiratory muscle mass is difficult to measure, we can use appendicular skeletal muscle mass as a surrogate. Probable respiratory sarcopenia is defined when respiratory muscle weakness and decreased appendicular skeletal muscle mass are observed. If only respiratory muscle strength is decreased without a decrease in respiratory function, the patient is diagnosed with possible respiratory sarcopenia. Respiratory muscle strength is assessed using maximum inspiratory pressure and maximum expiratory pressure. Ultrasonography and computed tomography are commonly used to assess respiratory muscle mass; however, there are insufficient data to propose the cutoff values for defining decreased respiratory muscle mass. It was jointly prepared by the representative authors and authorized by the Japanese Society for Respiratory Care and Rehabilitation, Japanese Association on Sarcopenia and Frailty, Japanese Society of Respiratory Physical Therapy and Japanese Association of Rehabilitation Nutrition. Geriatr Gerontol Int 2023; 23: 5–15.