Development and validation of severe muscle mass reduction cutoffs for GLIM Criteria in Japanese adults: A two‐phase study

Background The Global Leadership Initiative on Malnutrition prioritizes instrument‐based assessment of reduced muscle mass, but severity‐grading cutoffs for appendicular skeletal muscle mass index and fat‐free mass index are not established. We derived cutoffs for severe muscle mass reduction in older Japanese outpatients and examined their associations with mortality in hospitalized adults. Methods A frailty clinic registry identified thresholds for appendicular skeletal muscle mass index by dual‐energy X ‐ray absorptiometry or bioelectrical impedance analysis and fat‐free mass index by bioelectrical impedance analysis. Receiver operating characteristic analyses used 1‐year hospitalization as the outcome, with thresholds refined according to hospitalization risk. Nationwide claims data were used for validation. Mortality was assessed by Kaplan–Meier and Cox proportional hazards analyses adjusted for age, sex, comorbidities, and frailty. Results The development cohort included 1035 participants (mean age, 76.5 years). Severe muscle mass reduction cutoffs for appendicular skeletal muscle mass index were <6.4 kg/m 2 in men and <5.0 kg/m 2 in women using either method, and those for fat‐free mass index were <16.0 kg/m 2 in men and <13.4 kg/m 2 in women. In the validation cohort ( n = 242,464), severe muscle mass reduction was associated with higher mortality, with hazard ratios of 2.04 (95% confidence interval: 1.97–2.12), 1.95 (1.86–2.03), and 2.01 (1.94–2.09) for appendicular skeletal muscle mass index by dual‐energy X ‐ray absorptiometry and bioelectrical impedance analysis and for fat‐free mass index, respectively (all P < 0.001). Conclusion These cutoffs may facilitate severity grading according to the Global Leadership Initiative on Malnutrition criteria and improve prognostic risk stratification.