on Sarcopenia
To date, this is the most widely cited definition and the only definition that was endorsed by a range of international scientific societies (European Geriatric Medicine Society [EuGMS], European Society for Clinical Nutrition and Metabolism [ESPEN], International Association of Geriatrics and Gerontology‐European Region [IAGG‐ER], International Academy on Nutrition and Aging [IANA]) [13]. The European Working Group on Sarcopenia in Older People (EWGSOP) defined sarcopenia as a syndrome characterized by progressive and generalized loss of skeletal muscle mass and strength, with a risk of adverse outcomes such as physical disability, decreased quality of life, and increased mortality. According to the EWGSOP criteria, diagnosis of sarcopenia required documentation of low muscle mass plus documentation of either low muscle strength or low physical performance. With the aim of encouraging the assessment of sarcopenia in all patients and all health‐care settings, the EWGSOP provided a wide range of tools that made the assessment feasible even in settings with limited resources, including a suggested algorithm for case finding based on physical performance (usual gait speed) as the easiest and most reliable first step to begin sarcopenia screening in clinical practice. However, the EWGSOP found no evidence to recommend cut‐off points for each of the parameters used in the definition. The EWGSOP also suggested dividing sarcopenia into categories (primary or age‐related and secondary sarcopenia), and sarcopenia staging to reflect the severity of the condition.
The EWGSOP initiative was strongly supported by the Asian Working Group on Sarcopenia (AWGS) [15]. This group collected the best available evidence of sarcopenia research from Asian countries to establish the consensus for sarcopenia diagnosis and take an extra step forward by proposing gender‐specific cut‐off values for muscle mass estimation with DXA or bioimpedance analysis, handgrip strength, and usual gait speed. In addition to sarcopenia screening for community‐dwelling older people, the AWGS recommended sarcopenia assessment in certain clinical conditions and health‐care settings to facilitate implementing sarcopenia in clinical practice.
European Society for Clinical Nutrition and Metabolism Special Interest Groups
A special interest group on cachexia–anorexia in chronic wasting diseases was created in ESPEN, and the definition, assessment, and staging of cachexia were identified as a priority [12]. In the first consensus paper published by this group on the definition of cachexia and pre‐cachexia, the need of criteria for the differentiation between cachexia and other conditions associated with low muscle mass lead to a cooperation with the ESPEN special interest group on nutrition in geriatrics. Diagnosis of sarcopenia was defined by the combined presence of a low muscle mass (a percentage of muscle mass ≥2 standard deviations below the mean measured in young adults of the National Health and Nutrition Examination Survey [NHANES] population) and low gait speed.
Society for Sarcopenia, Cachexia and Wasting Disorders (SSCWD)
This organization conveyed American and European researchers to develop a definition of sarcopenia that could be a meaningful surrogate for clinically useful endpoints, allow for treatments, include only measurements longitudinally linked to meaningful outcomes, and have definable cut‐off points based on the data [10]. Deviating from the other groups, it was decided that “sarcopenia with limited mobility” would be the preferred term to define persons with a need for therapeutic interventions. Sarcopenia with limited mobility was defined as a muscle loss associated with a slow walking speed, with an approach that mirrored that proposed by ESPEN. The limitation in mobility should not be clearly attributable to the direct effect of specific diseases such as peripheral vascular disease, or central or peripheral nervous system disorders, dementia, or cachexia. This group left the question open of whether sarcopenia as a term should be limited to use in older persons or used as a general term for adults of any age.
International Working Group on Sarcopenia (IWGS)
A group of American and European geriatricians and scientists from academia and industry, some of them involved in other definitions, met in Italy at the end of 2009, to arrive at a consensus definition of sarcopenia. Sarcopenia was defined as the age‐associated loss of skeletal muscle mass and function [14]. It should be considered in all older patients who present with observed declines in physical function, strength, or overall health, and especially in those who are bedridden, cannot independently rise from a chair, or who have a slow gait speed. A reduced muscle mass would confirm sarcopenia in this clinical setting.
Foundation for the National Institutes of Health
A few years later, an American initiative led by the Foundation for the National Institutes of Health (FNIH) Biomarkers Consortium used a different approach, mostly based on the pooled analysis of epidemiological studies, to define sarcopenia [16]. This initiative compiled data from nine studies in community‐dwelling older persons, with a pooled sample of 26 625 participants, to identify sex‐specific cut‐off points for low muscle mass (estimated by the appendicular lean mass adjusted for body mass index) and low muscle strength (measured as grip strength). These cut‐off points were shown to be associated with functional limitations (including slow gait speed, used as a component of other definitions).
Both the AWGS and the FNIH tried to overcome a major limitation of the EWGSOP definition – it did not recommend explicit cut‐off points for the parameters included in the definition – by proposing precise references to define normality for each variable. However, all definitions at this time agreed on the overall concept of sarcopenia as a compound of low muscle mass and reduced muscle function, defined by muscle strength, reduced physical performance, or both. The role of muscle quality, although mentioned in some initiatives, was still quite unclear.
Some important milestones derived from these definitions have been, among others, the recognition of sarcopenia as an independent condition with an ICD‐10‐CM code in 2016 [17], the development of the first clinical guideline for the condition [18], and the involvement of the European Medicines Agency in initiatives to develop a framework for drug development [19].
MATURITY OF SARCOPENIA: RECENT DEFINITIONS
A decade later, the EWGSOP met again, with a wider academic support (adding the endorsement of International Osteoporosis Foundation [IOF] and European Society for Clinical and Economic Aspects of Osteoporosis, Osteoarthritis and Musculoskeletal Diseases [ESCEO] to ESPEN and EuGMS) to review and update the 2010 definition and reflect the advances in scientific, epidemiological, and clinical knowledge, and to facilitate the implementation of sarcopenia in mainstream clinical practice [20]. The updated consensus definition, named EWGSOP2, states that a person with low muscle strength and low muscle mass or quality will be diagnosed with sarcopenia. When sarcopenia impairs physical performance measures, it will be staged as severe sarcopenia. Sarcopenia is now understood as an organ (skeletal muscle) failure or insufficiency [21] that may appear acutely (in the setting of an acute disease or sudden immobility) or have a more chronic course. It aligns with the new function‐centered model proposed by the World Health Organization that focuses on intrinsic capacity (defined as a composite of all physical and mental capacities of an individual) [22].
The three main advances of the EWGSOP2 definition result from new insights: (i) sarcopenia is no longer considered primarily as a geriatric syndrome but as a muscle condition with an ICD‐CM diagnosis code (ICD‐10‐CM M62.84); (ii) loss of muscle quality is introduced as a new diagnostic criterion; and (iii) muscle strength is recognized as the best predictor of health outcomes. This definition intends to introduce sarcopenia in wide‐stream clinical practice as well, by offering a simple diagnostic algorithm. The AWGS has also published and updated definition [23]. Australia and New Zealand have opted to endorse the EWGSOP definitions [24]. Similar definitions focusing on the loss of strength or function in combination
