Arthritis is a prevalent inflammatory joint disorder that substantially increases disability and cardiovascular disease (CVD) risk. The C-reactive protein–triglyceride–glucose index (CTI) is an emerging marker reflecting immunometabolic dysfunction. However, the associations of baseline CTI, cumulative CTI exposure (cumCTI), and CTI change patterns in the development of CVD in arthritic populations remain unclear.

This study utilized data derived from the China Health and Retirement Longitudinal Study (CHARLS). CTI was calculated using biomarker data from two survey waves (2011–2012 and 2015–2016). CumCTI was defined as the time-weighted cumulative level across the two waves. CTI change patterns (two time points) were derived by K-means clustering of the two-wave CTI vector [CTI at Wave 1, CTI at Wave 3]. Multivariable Cox proportional-hazards models were employed to estimate the associations of baseline CTI, cumCTI, and CTI change patterns with incident CVD in middle-aged and older adults with arthritis. Restricted cubic splines (RCS) were employed to assess nonlinearity, and prespecified subgroup and sensitivity analyses were conducted to evaluate robustness.

The final study population comprised 1639 individuals. Among these, 486 (29.6%) were diagnosed with incident CVD during the follow-up period. Cluster analysis identified three CTI change patterns between 2012 and 2015. Multivariable cox regression analysis showed that for every unit increase in cumCTI, the risk of CVD increased by 12.3% (HR=1.123, 95%CI: 1.048-1.203, P=0.001). Compared with the lowest quartile, those in the highest cumCTI quartile had a 54.3% higher risk of CVD (HR = 1.543, 95% CI 1.155-2.061, P = 0.003; P for trend = 0.002). Participants with a moderate-increasing pattern had a 34.7% higher CVD risk compared with the low-stable group (HR = 1.347, 95% CI 1.084-1.674, P = 0.007). The association between cumCTI and CVD appeared linear (P for nonlinear = 0.801), whereas baseline CTI displayed marked nonlinearity with a threshold around 4.897 (P for nonlinear = 0.002). Subgroup analysis, interaction analyses and sensitivity analyses consistently supported the robustness of these associations.

In middle-aged and older adults with arthritis, both higher cumCTI exposure and unfavorable CTI change patterns were independently associated with increased CVD risk. CTI, readily obtainable from standard laboratory tests, may serve as a low-cost biomarker for early cardiovascular risk assessment and individualized prevention in this high-risk population.