As the aging population progresses, the importance of age-related diseases and conditions increases. With aging, skeletal muscle mass decreases, but functional decline in walking speed and grip strength is also observed. Sarcopenia is a risk factor for decreased activities of daily living (ADL),frailty, falls and fractures, hospitalization, institutionalization, and death, and its diagnostic criteria have been established in Europe, the United States, and Asia. In recent years, the EWGSOP published revised diagnostic criteria in 2018, followed by the AWGS, which revised its diagnostic criteria in October 2019. In the fi eld of respiratory and esophageal diseases, the diagnosis and treatment of sarcopenia are becoming increasingly important with the aging of the population, and management of sarcopenia according to the established guidelines is necessary to improve the quality of treatment.
Chronic obstructive pulmonary disease (COPD) is a common disease closely related to smoking. The natural progression of the disease is characterized by irreversible and gradually deteriorated obstructive dysfunction reflected by a decline in forced expiratory volume in 1 second (FEV1) accompanied by progressive dyspnea on exertion. Sarcopenia is a well-known comorbidity and is an important clinical feature for determining survival prognosis in patients with COPD. Multiple factors such as disuse, malnutrition, systemic inflammation, and physical inactivity might be involved in the decrease and weakness of the skeletal muscles. Approaches to induce behavioral changes that will lead to increase daily physical activity are of key importance for optimal management of patients with COPD.
Japan is aging at a very rapid pace unprecedented in human history. Recently, sarcopenia, which is a condition characterized by loss of muscle mass, muscle strength and muscle function, has attracted attention not only in the general population but also in patients with esophageal cancer. Sarcopenia has been reported to be a predictor for postoperative complications following esophagectomy and poor prognosis. In addition, sarcopenia in patients undergoing chemotherapy or chemoradiotherapy was reported to be associated with toxicity and termination of chemotherapy. To prevent loss of skeletal muscle and improve muscle strength and function, a combination of nutrition and exercise therapies was reported to be effective. The safety and efficacy of perioperative intervention for patients with esophageal cancer undergoing esophagectomy should be examined in future studies.
Sarcopenia is attracting attention today because it is associated with life prognosis, but the definition of sarcopenia has not been established. Until now, muscle mass reduction was considered an indispensable element of sarcopenia, but in 2019 EWGSOP announced that sarcopenia must firstly involve reduced muscle strength, adding that both muscle mass and muscle quality are important. We must also recognize the differences between disuse syndrome and sarcopenia. Although increasing reports are emerging of dysphagia due to sarcopenia, it is important to understand that general muscle sarcopenia and sarcopenia of swallowing muscles are different. The muscle related to swallowing is the striated muscle, but it is embryologically close to the respiratory muscle derived from the branchial arch and has characteristics different from those of the limb skeletal muscles. The swallowing muscle is difficult to become disused because it is driven by respiratory input at rest. The only exception is the geniohyoid muscle, which is prone to sarcopenia. While it is important to understand the dysphagia caused by sarcopenia of the swallowing muscles, many diseases that cause dysphagia in the elderly are complicated with sarcopenia, complicating the pathophysiology.
Sarcopenia is a serious concern in older adults, and several working groups for sarcopenia recommend using the presence of both low muscle strength and low muscle mass to diagnose sarcopenia. Numerous epidemiological studies have reported that sarcopenia is highly prevalent and is related to a high risk of mortality, disabilities, and loss of independence in older adults. The main approaches to prevention and treatment of sarcopenia are resistance training and protein intake. Several clinical trials indicate a combined program of resistance exercise and protein supplementation achieves significant improvement in muscle mass and strength.