Higher dietary inflammatory index predicts elevated risk of cardiometabolic–kidney syndrome: implications for preventive nutrition strategies

Abstract Background The American Heart Association (AHA) recently proposed the cardiovascular–kidney–metabolic (CKM) syndrome to unify cardiovascular, renal, and metabolic dysfunctions into a single framework. However, the relationship between the Dietary Inflammatory Index (DII) and CKM progression remains unclear. Leveraging data from the National Health and Nutrition Examination Survey (NHANES), this study investigated the dose–response relationship and potential heterogeneity between DII and CKM stages. Methods A total of 15,335 participants from the 2005–2018 NHANES cycles were included. CKM stages (0–4) were categorized following the AHA 2023 framework. DII scores were computed, and their associations with CKM stages were assessed using multivariable logistic regression, considering both continuous and quartile-based (Q1–Q4) DII measures. Restricted cubic spline (RCS) analysis was applied to explore nonlinear relationships, and subgroup analyses were conducted for sensitivity. Results In multivariable logistic regression analyses, higher DII was robustly associated with CKM progression in a dose–response manner. For each one-unit increase in the continuous DII, the odds of being in Stage 4 were 31% higher (OR = 1.31; 95% CI 1.04–1.65). In quartile analysis, the highest DII quartile (Q4) was associated with a 4.18-fold higher odds of Stage 4 compared to Q1 (OR = 4.18; 95% CI 1.65–10.6). RCS analysis showed a linear association between DII and CKM Stages 1, 2, and 4, whereas Stage 3 exhibited slightly reduced odds when DII > 1.5. Subgroup analyses indicated that higher DII was consistently linked with more severe CKM stages across most demographic and lifestyle factors. Conclusions Elevated DII scores substantially increase the risk of advanced CKM stages, with potential threshold effects. Behavioral factors (e.g., smoking and alcohol intake) and socioeconomic status may modify the DII–CKM relationship.