The Relationship Between Dietary Inflammatory Index and Intermediate‐to‐High‐Risk Cardiovascular‐Kidney‐Metabolic Syndrome and All‐Cause Mortality: The National Health and Nutrition Examination Survey 1999–2018: A Cross‐Sectional and Prospective Cohort Study

ABSTRACT Background The dietary inflammatory index (DII) score quantifies the inflammatory potential of an individual's diet and may be associated with cardiovascular–kidney–metabolic syndrome (CKM) and mortality risk. However, evidence on the relationship between DII and intermediate‐to‐high‐risk cardiovascular–kidney–metabolic syndrome (IH–CKM) is limited. Objective This study aimed to evaluate the association between DII and IH–CKM and to explore the relationship between DII and all‐cause mortality risk in individuals with and without IH–CKM. Methods We conducted a cross‐sectional and cohort analysis using data from the 1999–2018 National Health and Nutrition Examination Survey (NHANES). Weighted logistic regression models were used to examine associations between DII and IH–CKM, while weighted Cox proportional hazards models estimated hazard ratios (HRs) for all‐cause mortality. Restricted cubic spline analyses were employed to explore linear or nonlinear relationships. Results Among 38,732 participants, 30,421 had IH–CKM. Higher DII scores were positively associated with IH–CKM, with a fully adjusted odds ratio (OR) of 1.44 for the highest versus lowest quartile (95% CI: 1.27–1.63, p < 0.001). Regarding all‐cause mortality risk, each one‐unit increase in DII (range: −5.281 to 5.795) was associated with an adjusted HR of 1.04 (95% CI: 1.02–1.06, p < 0.001) in IH–CKM participants and 1.15 (95% CI: 1.06–1.26, p = 0.001) in non‐IH–CKM individuals. Conclusion Higher DII scores were positively associated with an increased risk of IH–CKM. In addition, elevated DII was linked to higher all‐cause mortality in both individuals with and without IH–CKM.