Association of cardiometabolic index with incident cardiovascular disease in middle-aged and older adults with cardiovascular-kidney-metabolic syndrome stages 0–3: evidence from CHARLS (2011–2020)

To examine the association between cardiometabolic index (CMI), including baseline CMI and cumulative average CMI (CumCMI), and the risk of cardiovascular disease (CVD) among Chinese middle-aged and older adults with Cardiovascular-Kidney-Metabolic (CKM) syndrome stages 0-3, and to explore its potential utility for risk assessment in this population. Data were derived from the China Health and Retirement Longitudinal Study (CHARLS, 2011-2020). A total of 6,991 participants aged ≥ 45 years with CKM syndrome stages 0-3 were included. Participants were categorized into quartiles according to CMI and CumCMI levels. Cox proportional hazards regression models with sequential adjustments were used to assess associations with incident CVD. Restricted cubic spline (RCS) models were applied to explore dose-response relationships. Subgroup and sensitivity analyses were conducted to assess the consistency of the findings. During a median follow-up of 10 years, 1599 (23.14%) participants developed CVD. In fully adjusted models, participants in the highest baseline CMI quartile (Q4) had a significantly higher risk of CVD compared with those in the lowest quartile (Q1) (HR = 1.347, 95% CI: 1.161-1.563; P for trend = 0.0001). Each 1-SD increase in baseline CMI was associated with a 8.0% higher CVD risk (HR = 1.080, 95% CI: 1.031-1.131). For CumCMI, Q4 versus Q1 was associated with a 40.9% higher CVD risk (HR = 1.409, 95% CI: 1.124-1.768), with a 11.5% increase in risk per 1-SD increment (HR = 1.115, 95% CI: 1.039-1.196). Restricted cubic spline (RCS) analyses revealed a significant non-linear association between CMI and CVD risk (Poverall < 0.001; Pnonlinear = 0.003), with a threshold value of 0.462. CMI showed statistically significant associations with incident stroke, but not with incident heart disease. Both baseline CMI and cumulative average CMI are independently associated with incident CVD among middle-aged and older adults with CKM syndrome stages 0-3, demonstrating a non-linear threshold relationship. Cumulative exposure to elevated CMI shows a stronger association with CVD risk, supporting the value of longitudinal assessment of cardiometabolic status for CVD risk assessment in this population.