Is Appendicular Lean Soft Tissue Mass a Clinically Valid Diagnostic Marker for Sarcopenia?

Aim Geriatric experts have long debated the inclusion of appendicular lean soft tissue mass (ALSTM) in the diagnostic criteria for sarcopenia. This study examined whether a diagnostic model for sarcopenia that excludes appendicular lean soft tissue mass (ALSTM) is equivalent to one that includes ALSTM in discriminating health‐related outcomes. Methods Community‐dwelling older adults from the Itabashi Longitudinal Study on Aging in Tokyo, Japan, were included. Based on the AWGS2019 criteria, we developed two diagnostic models: Model 1, including low handgrip strength/gait speed and low ALSTM assessed by bioelectrical impedance analysis, and Model 2, excluding low ALSTM. Health‐related outcomes were self‐reported falls and hospitalization in the past year. Differences in area under the receiver operating characteristic curve (AUC) and 95% confidence intervals (CI) between the two models were estimated using 1000 bootstrap samples. Results In total, 2432 participants (median age: 76 years; 53.2% men) without missing data were analyzed. Falls and hospitalization were reported by 17.8% and 15.3% of participants, respectively. The AUCs [95% CIs] of Models 1 and 2 were 0.61 [0.59, 0.64] and 0.61 [0.58, 0.64] for falls and 0.65 [0.62, 0.68] and 0.64 [0.61, 0.67] for hospitalization, respectively. The differences (Model 2—Model 1) in AUCs [95% CI] between the two models were −0.004 [−0.015, 0.006] for falls and −0.004 [−0.014, 0.004] for hospitalization, with the CIs within the pre‐specified equivalence margin (±0.05). Conclusions Diagnostic models excluding ALSTM demonstrated equivalent discrimination ability to those including ALSTM, raising questions about the necessity of ALSTM assessment for sarcopenia diagnosis.