Association of triglyceride glucose-body roundness index and body roundness index with incident sarcopenia among Chinese older adults: A nationwide cohort study

The relationship between TyG-BRI, BRI, and the sarcopenia definition proposed by the Asian Working Group for Sarcopenia (AWGS) in 2019 remains unclear. This research focused on exploring the relationship between the TyG-BRI index, BRI, and the incidence of sarcopenia among China's older population. Using multi-wave survey data from the China Health and Retirement Longitudinal Study (CHARLS) collected in 2011 and 2015, we followed 1946 participants without baseline sarcopenia. Incident sarcopenia and its components were identified using the Asian Working Group for Sarcopenia (AWGS) 2019 diagnostic algorithm . Multivariable logistic regression and restricted cubic splines were used to evaluate the independent associations of TyG-BRI and BRI, respectively, with incident sarcopenia and its diagnostic components. Subgroup analyses were also performed. The predictive performances of TyG-BRI and BRI were further compared using receiver operating characteristic (ROC) curves, net reclassification improvement (NRI), and integrated discrimination improvement (IDI). The E -value was used to quantify the impact of unmeasured confounders on the observed associations. After 4-year follow-up, sarcopenia was identified in 222 (11.4 %). Fully adjusted, both indices were inversely association with sarcopenia (TyG-BRI: OR = 0.97, 95 % CI 0.06–0.99, P = 0.003; BRI: OR = 0.77, 95 % CI 0.67–0.89, P < 0.001). For the components, higher TyG-BRI and BRI were linked to lower odds of low muscle mass (TyG-BRI: OR = 0.97, 95 % CI 0.95–0.98, P < 0.001; BRI: OR = 0.72, 95 % CI 0.63–0.83, P < 0.001) but higher odds of muscle strength(TyG-BRI: OR = 1.03, 95 % CI 1.01–1.05, P = 0.006; BRI: OR = 1.26, 95 % CI 1.05–1.51, P = 0.011).Only TyG-BRI was modestly associated with impaired physical performance (OR = 1.01, 95 % CI 1.00–1.03, P = 0.042); BRI was not (OR = 1.12, 95 % CI 0.99–1.28, P = 0.072). RCS analysis showed linear dose–response relationships for both TyG-BRI and BRI with sarcopenia. Additionally, ROC analysis, NRI, and IDI indicated that TyG-BRI provided no incremental predictive value over BRI. Our results indicated that elevated levels of TyG-BRI and BRI are independently associated with decreased risk of sarcopenia. Furthermore, TyG-BRI failed to improve predictive performance for sarcopenia when compared with BRI alone. Collectively, these findings highlight the necessity of integrating adipose tissue assessments in sarcopenia evaluation for older adults. • Higher TyG-BRI and BRI are linked to a lower risk of sarcopenia in older Chinese adults. • Higher TyG-BRI and BRI exhibited inverse associations with muscle mass, this does not translate to improved muscle strength or physical performance. • BRI alone predicts sarcopenia risk effectively, with no additional value from TyG-BRI.