Abstract
BACKGROUND: Sarcopenic obesity (SO) combines reduced muscle mass and increased fat, elevating health risks in older adults. The triglyceride-glucose (TyG) index, a marker of insulin resistance, is associated with metabolic dysfunction. However, its role in predicting mortality in SO remains unclear. This study investigates the TyG index as a potential predictor of all-cause mortality in older adults with SO. METHODS: This study examined SO trends using data from 30,137 adults with dual-energy X-ray absorptiometry (DXA) and body fat measurements (1999-2018). For mortality analysis, 706 participants from NHANES 1999-2004 were included. Sarcopenia was defined according to the 2014 FNIH criteria. Statistical analyses, including Cox regression, cubic splines, and subgroup analyses, were employed to investigate the association between the TyG index and all-cause mortality in SO, as well as mortality variations among NHANES participants. RESULTS: Older age groups exhibit higher SO prevalence rates, with a notable upward trend in the >70 years group, while younger groups maintain lower rates. Trend analysis indicates no significant change from 1999 to 2006 but suggests a moderate, near-significant increase from 2011 to 2018. There was a U-shaped association between the TyG index and all-cause mortality. After full adjustment, adults in TyG group 1 (less than 3.25) had a 78.1 % higher risk (hazard ratio, 1.781; 95 % CI, 1.406-2.256; p < 0.001), and those in TyG group 5 (6.66 or greater) had a 74.5 % higher risk (hazard ratio, 1.745; 95 % CI, 1.211-2.516; p = 0.003) compared to the reference group (TyG group 3, 4.25 to 5.25). Subgroup analysis by age revealed that, among participants aged 70 and older, the group with the lowest mortality risk transitioned from Group 3 to Group 2. Furthermore, the analysis of varying mortality reveals that Group 5 (HR: 3.088; 95 % CI: 1.462-6.520; p = 0.003) is significantly associated with an increased risk of cardiovascular disease (CVD) mortality compared to Group 3. Similarly, TyG Group 1 demonstrates a significantly higher risk of mortality from other causes (HR: 2.253; 95 % CI: 1.207-4.206; p = 0.011) relative to Group 3. No significant associations are observed for malignant neoplasms, respiratory diseases, or cerebrovascular/Alzheimer's diseases. CONCLUSION: This national cohort study identified a U-shaped association between the TyG index and all-cause mortality among SO patients, with increased risks observed at both low and high TyG levels. Age-specific analyses further reveal variations in this relationship, underscoring the importance of tailored strategies to enhance metabolic health and reduce mortality risks.