Respiratory Sarcopenia and Sarcopenic Respiratory Disability: Concepts, Diagnosis, and Treatment

Abstract

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.

Keywords: Rehabilitation nutrition; aging; muscle wasting; respiration; secondary sarcopenia.

Figure 1

Vicious cycle of respiratory sarcopenia and sarcopenic respiratory disability and intervention of combined exercise and nutrition Aging, low activity, undernutrition, inflammation, and iatrogenic causes are etiologies of whole-body sarcopenia and respiratory sarcopenia. Whole-body sarcopenia and respiratory sarcopenia further exacerbate low activity, undernutrition, and inflammation. The vicious cycle results in sarcopenic respiratory disability. Rehabilitation nutrition is presumed to be effective for treating respiratory sarcopenia and sarcopenic respiratory disability, and may break the vicious cycle of respiratory sarcopenia and sarcopenic respiratory disability. a) Exercise, b) Nutrition, c) Exercise + Nutrition (Rehabilitation Nutrition)

Figure 2

A flow-chart for diagnosing respiratory sarcopenia “Definite sarcopenia” is diagnosed when whole-body sarcopenia with low respiratory muscle mass is identified followed by low respiratory muscle strength and/or deteriorated respiratory function with the exclusion of obvious disease causative of low respiratory muscle mass. Cases where other criteria are met alone (respiratory muscle mass measurement is excluded) are diagnosed as “probable respiratory sarcopenia.” Cases with possible diseases causative of respiratory dysfunction are diagnosed as “possible respiratory sarcopenia.” Abbreviations: EWGSOP, European Working Group on Sarcopenia in Older People; AWGS, Asian Working Group of Sarcopenia; ATS/ERS, American Thoracic Society/European Respiratory Society; Wt, weight

Figure 3

Diagnosis of sarcopenic respiratory disability Sarcopenic respiratory disability is diagnosed as respiratory sarcopenia with functional disability. Functional disability is assessed using a modified Medical Research Council of grade 2 or more. Cases of respiratory sarcopenia without functional disability are diagnosed as “at risk of sarcopenic respiratory disability.” Presbypnea is a possible cause of sarcopenic respiratory disability in older people. On the other hand, respiratory diseases may be possible causes of sarcopenic respiratory disability in the young. When functional disability is present in the absence of respiratory sarcopenia, the cause is considered to be other respiratory diseases.