Association between the Dietary Index for Gut Microbiota and cognitive function among older adults in the United States

BackgroundThe Dietary Index for Gut Microbiota (DI-GM) is a novel index reflecting diet quality relative to gut microbiota health.ObjectiveThe study aims to investigate the relationship between DI-GM and cognitive function in older adults.MethodsData were obtained from 2629 participants aged ≥60 years in the National Health and Nutrition Examination Surveys (NHANES) (2011-2014). Cognitive function was assessed using the Consortium to Establish a Registry for Alzheimer's Disease (CERAD), the Animal Fluency Test (AFT), the Digit Symbol Substitution Test (DSST), and a global z score. Multivariable linear regression, restricted cubic splines (RCS), and subgroup analysis were performed. Predictive utility of DI-GM was assessed via the receiver operating characteristic (ROC) analysis against a baseline model. Mediation analysis examined relationships among DI-GM, the Dietary Inflammatory Index (DII), and cognitive outcomes.ResultsHigher DI-GM was associated with higher AFT, DSST, and the global z scores (p < 0.001). After full adjustment, participants with DI-GM (≥ 6) showed higher AFT score (β = 1.11, 95% CI 0.46∼1.75), DSST score (β = 4.95, 95% CI 3.05∼6.86) and z score (β = 0.19, 95% CI 0.10∼0.28), compared to those with DI-GM (0-3). No significant direct association was observed with CERAD (β = 0.45, 95% CI -0.29∼1.18, p = 0.233). RCS indicated linear relationships between DI-GM and cognitive function scores. DI-GM had excellent predictive performances based on the ROC. No significant interactions were detected by subgroup analysis. Furthermore, DII partly mediated the relationship between DI-GM and cognitive function.ConclusionsThe DI-GM showed a linear positive correlation with cognitive function in older adults.