Definitions, diagnostic criteria and assessment methods used in the diagnosis of sarcopenia: a scoping review.
BACKGROUND & AIMS The definition of sarcopenia has evolved substantially since its original operationalization as a muscle mass phenomenon. Multiple definitions have been proposed over the past decades, incorporating muscle strength and physical performance, yet no universally accepted diagnostic standard exists. This scoping review aimed to map and summarize the definitions, diagnostic criteria, assessment methods, and epidemiological patterns of sarcopenia in middle-aged and older adult populations. METHODS In order to capture the first 25 years of research, PubMed/MEDLINE, Embase, and Web of Science were searched from January 1998 to December 2023. Eligible studies were peer-reviewed articles that explicitly described how sarcopenia was diagnosed in populations with a mean or median age of at least 50 years. Data extraction was performed using a standardized chart, supported by a locally deployed large language model, with systematic dual-reviewer verification of all extracted data. RESULTS A total of 4,578 publications were included, yielding 5,241 sarcopenia-definition instances and more than 21 million cumulative participant records. Publication volume increased markedly over time. The literature was geographically concentrated in East Asia, Europe and North America. Nearly all definitions were categorized into one of five taxonomic groups: muscle mass combined with function, muscle mass alone, function alone, risk assessment tools, and clinical classification. Definitions combining muscle mass plus function were the most frequently used (54.5%), with EWGSOP and AWGS criteria predominating, followed by muscle mass definitions (41.9%). Mass-only definitions nevertheless remained prominent in specialties relying heavily on computed tomography, particularly oncology. Muscle mass was assessed in 96.3% of studies, most commonly via bioelectrical impedance analysis, dual-energy X-ray absorptiometry, and computed tomography. Handgrip strength and gait speed were the most widely used functional measures. CONCLUSIONS Sarcopenia research has grown rapidly, but remains highly heterogeneous in its operationalization. Although consensus definitions have supported a shift toward multidimensional assessment, methodological variability continues to limit comparability between studies. Until a unified definition of sarcopenia is globally accepted, literature should explicitly report the definition applied, the instruments and protocols used to assess each component, and the thresholds adopted in order to enable meaningful cross-study comparability.