Association Between Composite Dietary Antioxidant Index and Cognitive Function Among Aging Americans from NHANES 2011–2014

Background: Antioxidant diets are considered to be protective factors for cognitive function. However, comprehensive measures of antioxidant diets are lacking. Objective: To examine the association between the Composite Dietary Antioxidant Index (CDAI) and cognitive function in the elderly. Methods: This cross-sectional study included a total of 2,456 participants (≥60 years old) from NHANES 2011–2014. Calculation of CDAI based on 6 minerals and vitamins (manganese, selenium, zinc, vitamins A, C, and E). Cognitive function was measured by the Consortium to Establish a Registry for Alzheimer’s Disease (CERAD) Word Learning sub-test, Animal Fluency Test (AFT), and Digit Symbol Substitution Test (DSST). We also created a composite cognitive z-score to represent global cognition. The statistical analyses we used included multiple linear regression analyses, subgroup analyses, curve-fitting analyses, and threshold effects analyses. Results: After controlling for demographic characteristics, lifestyle factors, and disease history, multivariate linear regression analyses showed that increased CDAI was positively associated with scores on global cognitive function and each cognitive domain (p < 0.05), with subgroup analyses suggesting that this association was more pronounced in stroke patients (p for interaction < 0.05). Curve-fitting analyses and threshold effect analyses showed saturation effects between CDAI and CREAD Test, AFT, and composite Z-score, and an inverted U-shaped relationship with DSST, with inflection points of –1.89, 0.79, 1.13, and 1.77, respectively. Conclusions: Our findings support that higher levels of CDAI are correlated with significantly elevated cognitive function. Maintaining CDAI in an appropriate range may contribute to cognitive health in elderly.