Abstract
BACKGROUND: This study utilizes data from two principal sources: the National Health and Nutrition Examination Survey (NHANES) conducted in the United States from 1999 to 2020 and the China Health and Retirement Longitudinal Study (CHARLS) from 2011. This study examines the association between cardiometabolic index (CMI) and hypertension–diabetes comorbidity among individuals aged 45 years and older in the general population. Clarifying this relationship is important for developing effective prevention and management strategies for hypertension and diabetes in middle-aged and older individuals. METHODS: This study utilized data from NHANES (1999–2020) and CHARLS (2011) to conduct a cross-sectional analysis. The study population comprised adults aged 45 years and older from the general population. The cardiometabolic index (CMI) was calculated using the waist-to-height ratio and the triglycerides-to-high-density lipoprotein cholesterol (HDL-C) ratio. Weighted multivariate logistic regression analyses were employed to assess the association between LnCMI and the likelihood of hypertension–diabetes comorbidity, while adjusting for potential confounders. Subgroup analyses, restricted cubic spline (RCS), interaction tests, threshold effect analyses, and sensitivity analyses were performed. RESULTS: Associations were observed in both databases between LnCMI and the prevalence of hypertension–diabetes comorbidity in adults aged 45 years and older. In CHARLS, the fully adjusted logistic regression model showed a positive association between higher LnCMI and hypertension–diabetes comorbidity (OR = 1.760, 95% CI: 1.574–1.964), with a threshold value of 0.121. In ROC analyses, CMI showed the highest discriminative performance among the tested indices in CHARLS (AUC = 0.739). In NHANES, the survey-weighted fully adjusted logistic regression model also showed a positive association between higher LnCMI and the odds of hypertension–diabetes comorbidity (OR = 1.995, 95% CI: 1.794–2.218), with a threshold value of 0.286. Subgroup analyses suggested that sex and smoking status modified the association between LnCMI and hypertension–diabetes comorbidity. CONCLUSIONS: In these cross-sectional surveys, LnCMI was associated with hypertension–diabetes comorbidity prevalence and may be a useful marker for population prevalence stratification in China and the United States. CLINICAL TRIAL NUMBER: Not applicable. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12902-026-02177-2.