Association between different dimensions of C-reactive protein-triglyceride-glucose index and the incidence of frailty in middle-aged and elderly adults in China: A nationwide prospective cohort study

Background: Inflammation and metabolic disorders significantly contribute to frailty development. The C-reactive protein-triglyceride-glucose index (CTI) indicates both inflammation and insulin resistance (IR). This study delves into the connection between various dimensions of CTI—baseline CTI, cumulative CTI (cumCTI), and CTI change—and the incidence of frailty among the Chinese middle-aged and elderly demographic. Methods: This research employed the China Health and Retirement Longitudinal Study (CHARLS). K-means clustering was utilized to categorize the dynamic variations in CTI. The connection between various CTI dimensions and the frailty risk was evaluated through the Cox proportional hazards model and restricted cubic spline (RCS) regression model. Subgroup analyses, interaction tests, and sensitivity analyses were performed to ensure result robustness. Results: The research involved a total of 5,366 participants. Through the application of K-means clustering, 3 classifications of changes in CTI trajectories were identified. Baseline characteristics from the K-means clustering analysis showed that the median age of individuals was 58 years (52, 64). Within the studied group, there were 2,899 males, constituting 54.0% of the total sample. During follow-up, there were 964 newly identified instances of frailty, accounting for 18.0% of the total cases documented. A notable positive linear correlation between increased CTI levels and the likelihood of experiencing frailty. In Model 3, each unit increment in the baseline CTI was associated with a 34.6% escalation in the likelihood of frailty (HR, 1.346; 95% CI, 1.208–1.499). Furthermore, each additional unit of cumCTI was linked to a 13.9% escalation in frailty risk (HR, 1.139; 95% CI, 1.093–1.187).The RCS analysis revealed a positive linear correlation between the initial CTI, cumCTI, and the likelihood of developing frailty. Subgroup and interaction analyses did not demonstrate any significant variations among the different subgroups ( P >0.05). Sensitivity analyses further validated the consistency and reliability of these findings. Conclusion: Elevated CTI are linked to an increased likelihood of frailty. Ongoing longitudinal assessment of CTI levels across multiple dimensions can facilitate the timely detection of patients who are at a significant risk of developing frailty.