A serum creatinine–cystatin C-derived index as a predictive marker for sarcopenia incidence and progression in community-dwelling older adults: a prospective cohort study

BACKGROUND: Identifying individuals at risk of sarcopenia incidence or progression remains challenging. Serum creatinine- and cystatin C-derived indices are objective markers of muscle metabolism; however, their predictive value for sarcopenia progression remains uncertain. This study evaluated the association between a creatinine- and cystatin C-derived index, the total body muscle mass index (TBMM) and sarcopenia incidence or progression in community-dwelling older adults. METHODS: This prospective cohort study included 671 older adults (median age 72 [IQR 68-76] years; 35.0% male). Sarcopenia was diagnosed using the Asian Working Group for Sarcopenia criteria. Participants were stratified by sex-specific tertiles of TBMM. The outcome was defined as incident or progressive sarcopenia, with progression defined as the development of severe sarcopenia in those affected at baseline. Cox proportional hazards regression models and time-dependent receiver operating characteristic curve analyses were used to assess the associations. RESULTS: During follow-up, 7.5% of participants experienced sarcopenia incidence or progression. Higher TBMM tertiles were significantly associated with a lower risk, with adjusted hazard ratios of 0.18 (95% confidence interval [CI]: 0.07-0.42; P < .001) and 0.15 (95% CI: 0.06-0.40; P < .001) for Tertiles 2 and 3, respectively, compared with Tertile 1. Incorporating TBMM into predictive models improved discrimination (area under the curve increased from 0.771 to 0.856, P = .01). CONCLUSIONS: TBMM is a strong predictor of sarcopenia incidence and progression in community-dwelling older adults. Given its accessibility and accuracy, TBMM may serve as a valuable tool for early risk stratification and timely interventions in clinical practice.