Association of the cardiometabolic index and depressive symptoms with cardiovascular disease in cardiovascular-kidney-metabolic syndrome stages 0–3: A prospective cohort study

The progressive nature of cardiovascular-kidney-metabolic syndrome (CKM) allows early intervention during stages 0–3. However, the role of the cardiometabolic index (CMI) across CKM stages 0–3 and its potential synergy with depressive symptoms remain unclear. We followed 5,556 CHARLS participants (aged ≥ 45, CKM stages 0–3) for 7 years. Higher CMI and cumulative average CMI (CumCMI) were independently associated with CVD (HR for Q4 vs. Q1: 1.27, P trend = 0.009; HR for high vs. low CumCMI: 1.28, P trend < 0.001). Nonlinear thresholds were 0.47 (CMI) and 2.08 (CumCMI). Among 2,595 participants with complete depressive symptoms data, those with high CumCMI alone (HR = 1.61) or depressive symptoms alone (HR = 1.43) had elevated risk, whereas those with both factors had the highest risk (HR = 2.08). Baseline AUC was 0.651; adding CMI alone yielded no improvement (0.651), whereas adding depressive symptoms alone raised it to 0.657; both together gave 0.657–0.658. However, additive interaction was not statistically significant, and the AUC improvement from adding depressive symptoms to a model already containing CMI was minimal (ΔAUC ≈ 0.007), suggesting that this combined indicator may be more suitable for population-level risk stratification than individual clinical prediction.