Association between modified cardiometabolic index and stroke events among individuals with overweight or obesity across cardiovascular-kidney-metabolic syndrome stages 1–4: a prospective cohort study

Metabolic dysfunction induced by overweight and obesity is a pivotal driver of stroke and substantially increases the public health burden among middle-aged and older adults in China.The newly proposed Cardiovascular-Kidney-Metabolic(CKM) syndrome framework offers a conceptual risk-stratification perspective for exploring the prevention and control of metabolic-related cerebrovascular diseases.However, simple, accurate, and scalable risk stratification tools tailored to this framework remain insufficient in clinical practice. As a comprehensive metabolic indicator, the modified cardiometabolic index integrates abdominal obesity, lipid disorders, and insulin resistance, enabling overall quantification of systemic metabolic load with superior completeness compared with traditional single metabolic markers. Nevertheless, its long-term predictive value for stroke risk in overweight and obese populations remains unclear. This study aimed to explore the association and dose–response relationship between the modified cardiometabolic index and incident stroke, so as to support precise primary stroke prevention. Based on the nationally representative prospective China Health and Retirement Longitudinal Study (CHARLS), this study ultimately enrolled 2749 middle-aged and older overweight or obese adults across CKM stages 1–4 and free of baseline stroke. Notably, CKM stage 4 includes individuals with established clinical cardiovascular diseases, and we strictly excluded only participants with prior stroke while retaining those with other non-stroke cardiovascular comorbidities.The baseline modified cardiometabolic index was calculated using anthropometric and biochemical parameters. Multivariate Cox proportional hazard regression models were constructed to evaluate the independent association between the index and stroke incidence. Restricted cubic spline analysis was performed to fit the dose–response curve. Kaplan–Meier survival analysis, subgroup stratification, and sensitivity analysis were adopted to verify result robustness. A total of 2749 overweight/obese participants aged ≥ 45 years with CKM stage 1–4 were enrolled in the present study, of whom 61.3% were male. A total of 213 incident stroke events (7.7%) were documented during follow-up. Violin plots showed that baseline MCMI levels were significantly higher among participants who developed stroke than those without stroke ( P < 0.05). After full adjustment for multiple covariates, per 1-unit increment in continuous MCMI was not significantly associated with stroke risk (HR = 0.97, 95% CI: 0.74–1.27, P = 0.811).However, categorical quartile-based analyses revealed significant graded risk differences across MCMI subgroups. MCMI was further categorized into quartiles with Q1 as the reference group. The fully adjusted HRs for Q2, Q3, and Q4 were 1.36 (95% CI: 0.81–2.27, P = 0.249), 1.98 (95% CI: 1.15–3.42, P < 0.05), and 2.63 (95% CI: 1.46–4.74, P < 0.001), respectively, with a significant linear trend across quartiles (P for trend < 0.05). Kaplan–Meier curves demonstrated stepwise elevated cumulative stroke risk from Q1 to Q4, with a significant log-rank difference between groups ( P < 0.0001). Restricted cubic spline analyses identified a significant overall association between MCMI and stroke risk (P for overall = 0.007), while the nonlinear association was non-significant (P for nonlinear = 0.171), with a visually observed inflection-like location at MCMI = 3.32. Subgroup interaction analyses suggested that the observed graded positive association between MCMI and stroke risk may be consistent across all strata of sex, drinking status, smoking status, hypertension, diabetes, age, and CKM stage (all P for interaction > 0.05), while BMI category provided suggestive evidence for potential effect-heterogeneity between overweight and obese subgroups within this cohort (P for interaction = 0.015). This study identified a significant linear dose-response association between MCMI and elevated incident stroke risk among overweight/obese adults with CKM stages 1–4, with a visually observed inflection-like location at MCMI = 3.32, while no statistically significant nonlinear relationship was observed. These findings suggest that MCMI may serve as a practical biomarker for risk stratification within this high-risk population.