To investigate the longitudinal association between long-term levels of the C-reactive protein-triglyceride-glucose index (CTI) and changes in sarcopenia status among middle-aged and older adults in China.

This study was based on data from the baseline survey and the second follow-up of the China Health and Retirement Longitudinal Study (CHARLS). Long-term CTI levels were characterized using k-means clustering-derived categories and cumulative CTI. Changes in sarcopenia status were defined according to sarcopenia status at baseline and at follow-up. Multivariable logistic regression models were used to examine longitudinal associations. Stratified analyses were performed, and dose–response relationships were assessed using restricted cubic spline models.

A total of 3 377 middle-aged and older participants who met the inclusion and exclusion criteria were included in the analysis. K-means clustering classified long-term CTI levels into three groups: persistently low, persistently moderate, and persistently high. Compared with the persistently low CTI group, individuals with persistently high CTI levels had a significantly higher risk of sarcopenia progression (OR=1.66, 95%CI: 1.07~2.57; P<0.05), with generally consistent directions across subgroups. Using the median cumulative CTI (14.29) as the reference, the risk of sarcopenia progression initially decreased and then increased with increasing cumulative CTI, with a elevation in risk within the range of 15~17. The highest risk was approximately 1.53 times that of the reference value (OR=1.53, 95%CI: 1.17~1.99; P<0.05).

Among middle-aged and older adults in China, persistently high long-term CTI levels are associated with an increased risk of sarcopenia progression, providing epidemiological evidence to support the prevention of the onset and progression of sarcopenia.