Combined associations of triglyceride-glucose index and biochemical sarcopenia index with cardiometabolic multimorbidity in middle-aged and older Chinese adults.

Background

Cardiometabolic multimorbidity confers a substantial disease burden in middle-aged and older adults. The triglyceride-glucose index is a reliable marker of insulin resistance, while the biochemical sarcopenia index reflects skeletal muscle mass. However, their combined association with cardiometabolic multimorbidity remains unclear.

Methods

Based on the China Health and Retirement Longitudinal Study prospective cohort, we included 6092 participants aged ≥45 years. Cox regression, restricted cubic spline, time-dependent receiver operating characteristic curves, and interaction analyses were performed to examine the associations of triglyceride-glucose index, biochemical sarcopenia index, and a composite index with incident cardiometabolic multimorbidity, as well as predictive performance and effect modification.

Results

During a mean 9.27-year follow-up, there were 652 incident cases of cardiometabolic multimorbidity. The triglyceride-glucose index and composite index were independently associated with a higher risk of cardiometabolic multimorbidity (both P < 0.001), whereas the biochemical sarcopenia index showed no longitudinal predictive value after full adjustment. No significant additive or multiplicative interaction was observed between the TyG index and SI (RERI = 0.005, 95% CI -0.512 to 0.522; AP = 0.003, 95% CI -0.270 to 0.275; S = 1.006, 95% CI 0.892 to 1.134). Predictive performance of all indices gradually declined with longer follow-up.

Conclusion

The triglyceride-glucose index is a robust and independent predictor of incident cardiometabolic multimorbidity. A composite index derived from a principal component analysis showed a very small incremental improvement over the TyG index alone (ΔAUC = 0.006), though the clinical significance of this difference is uncertain and requires external validation.