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.

Malnutrition and sarcopenia often occur in rehabilitation settings. The prevalence of malnutrition and sarcopenia in older patients undergoing rehabilitation is 49–67 % and 40–46.5 %, respectively. Malnutrition and sarcopenia are associated with poorer rehabilitation outcome and physical function. Therefore, a combination of both rehabilitation and nutrition care management may improve outcome in disabled elderly with malnutrition and sarcopenia. The concept of rehabilitation nutrition as a combination of both rehabilitation and nutrition care management and the International Classification of Functioning, Disability and Health guidelines are used to evaluate nutrition status and to maximize functionality in the elderly and other people with disability. Assessment of the multifactorial causes of primary and secondary sarcopenia is important because rehabilitation nutrition for sarcopenia differs depending on its etiology. Treatment of age‐related sarcopenia should include resistance training and dietary supplements of amino acids. Therapy for activity‐related sarcopenia includes reduced bed rest time and early mobilization and physical activity. Treatment for disease‐related sarcopenia requires therapies for advanced organ failure, inflammatory disease, malignancy, or endocrine disease, while therapy for nutrition‐related sarcopenia involves appropriate nutrition management to increase muscle mass. Because primary and secondary sarcopenia often coexist in people with disability, the concept of rehabilitation nutrition is useful for their treatment. Stroke, hip fracture, and hospital‐associated deconditioning are major causes of disability, and inpatients of rehabilitation facilities often have malnutrition and sarcopenia. We review the concept of rehabilitation nutrition, the rehabilitation nutrition options for stroke, hip fracture, hospital‐associated deconditioning, sarcopenic dysphagia, and then evaluate the amount of research interest in rehabilitation nutrition.

The condition of muscle fiber atrophy and weakness that occurs in respiratory muscles along with systemic skeletal muscle with age is known as respiratory sarcopenia. The Japanese Working Group of Respiratory Sarcopenia of the Japanese Association of Rehabilitation Nutrition narratively reviews these areas, and proposes the concept and diagnostic criteria. We have defined respiratory sarcopenia as “whole-body sarcopenia and low respiratory muscle mass followed by low respiratory muscle strength and/or low respiratory function.” Respiratory sarcopenia can be caused by various factors such as aging, decreased activity, undernutrition, disease, cachexia, and iatrogenic causes. We have also created an algorithm for diagnosing respiratory sarcopenia. Respiratory function decreases with age in healthy older people, along with low respiratory muscle mass and strength. We have created a new term, “Presbypnea,” meaning a decline in respiratory function with aging. Minor functional respiratory disability due to aging, such as that indicated by a modified Medical Research Council level 1 (troubled by shortness of breath when hurrying or walking straight up hill), is an indicator of presbypnea. We also define sarcopenic respiratory disability as “a disability with deteriorated respiratory function that results from respiratory sarcopenia.” Sarcopenic respiratory disability is diagnosed if respiratory sarcopenia is present with functional disability. Cases of respiratory sarcopenia without functional disability are diagnosed as “at risk of sarcopenic respiratory disability.” Functional disability is defined as a modified Medical Research Council grade of 2 or more. Rehabilitation nutrition, treatment that combines rehabilitation and nutritional management, may be adequate to prevent and treat respiratory sarcopenia and sarcopenic respiratory disability.

Anamorelin is a ghrelin receptor agonist that can be administered orally and thought to improve cancer cachexia by improving appetite and increasing serum insulin‐like growth factor‐1. Anamorelin was not approved for use in Europe. In contrast, the use of anamorelin for cancer cachexia in four types of cancer (non‐small cell lung cancer, gastric cancer, pancreatic cancer, and colorectal cancer) was approved in Japan on 11 December 2020. Phase 2 trial (ONO‐7643‐04) for the treatment of patients with non‐small cell lung cancer and cachexia resulted in 1.56 kg lean body mass increase assessed by dual‐energy X‐ray absorptiometry (DXA). Another study for advanced and unresectable gastrointestinal (colorectal, gastric, or pancreatic) cancer showed 1.89 ± 0.36 kg improvement in lean body mass. Skeletal lean body mass assessed by DXA is important for diagnosing sarcopenia and cachexia in Asia. The approval of anamorelin is expected to change clinical practice of cancer cachexia in Japan and hopefully in other countries. In the past, cachexia was rarely diagnosed in Japan, because it was often thought that cachexia meant terminal stage. The dissemination of clinical findings on anamorelin from Japan, as well as the creation of consensus papers and clinical practice guidelines for cachexia in Japan and Asia, will be required to promote international expansion in the future.