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.