Respiratory Sarcopenia: Current Understanding of Concepts and Future Issues

The concept of “respiratory sarcopenia” originates from traditional sarcopenia, with the first definition introduced in 2019 using peak expiratory flow rate (PEFR).1 Because of challenges in assessing respiratory muscles and the lack of clinical instruments to measure respiratory muscle strength, PEFR was proposed as the defining metric. Recently, the Japanese Working Group for Respiratory Sarcopenia (JWGRS), consisting of 4 professional organizations, developed new diagnostic criteria for respiratory sarcopenia,2 defining it as reduced respiratory muscle strength, separate from “whole-body sarcopenia,” and classifying it into 4 severity levels: respiratory sarcopenia, probable sarcopenia, possible respiratory sarcopenia, and respiratory muscle weakness because of respiratory dysfunction (Table 1).