Association of sarcopenia index with fall risk in older adults with impaired renal function: A cohort study based on CHARLS data

This secondary analysis explored the association between the sarcopenia index (SI), calculated using serum creatinine and cystatin C values, and fall risk in middle aged and older adults with impaired renal function (estimated glomerular filtration rate < 90 mL/min/1.73 m²). Data from the 2011 baseline and 2015 follow-up cohorts of the China Health and Retirement Longitudinal Study were analyzed. Impaired renal function was defined using estimated glomerular filtration rate values, and the SI was derived as the product of serum creatinine and cystatin C-based estimated glomerular filtration rate. Falls were assessed using self-reported questionnaires during follow-up. Multivariate logistic regression and restricted cubic spline models were used to evaluate the SI-fall relationship, and subgroup analyses identified high-risk populations. Among 3461 participants, 20.8% reported falls. Higher SIs were associated with fewer falls, with adjusted odds ratios (95% confidence interval) for Q2, Q3, and Q4 of 0.75 (0.57-0.99), 0.66 (0.46-0.93), and 0.54 (0.31-0.93) versus Q1, respectively. The restricted cubic spline analysis indicated no dose-response relationship (P, overall = .312). Stratified analyses revealed a pronounced protective effect in individuals with obesity (odds ratio: 0.57, 95% confidence interval: 0.36-0.92; P, interaction = .039). SI was inversely associated with fall risk in older adults with impaired renal function, particularly in those with obesity. These findings support the use of SI as a practical biomarker for identifying high-risk individuals and developing targeted fall prevention strategies.