Association between composite dietary antioxidant index and cognitive function impairment among the US older adults: a cross-sectional study based on the NHANES 2011-2014.

Background: Cognitive function impairment (CFI) and the Composite Dietary Antioxidant Index (CDAI) were investigated in this study.

Methods: Participants from the 2011-2014 cycles of the National Health and Nutrition Examination Survey were chosen to assess cognitive function using the Consortium to Establish a Registry for Alzheimer's Disease Word Learning Test, the Animal Fluency Test, and the Digit Symbol Substitution Test. Participants scored below the 25% percentile of any of the three tests were defined as having cognitive function impairment. 24-h recalls of diet were collected to calculate CDAI.

Results: 2,424 participants were included. The fully adjusted multivariate logistic regression model showed an increase of one CDAI unit reduced CFI risk by 5% (95% CI: 0.92 ~ 0.98,  = 0.004). When comparing individuals with the lowest CDAI in the first quartile (<-2.42), the adjusted odds ratio for CDAI and CFI were 0.81 (95% CI: 0.61 ~ 1.06,  = 0.125) in the second quartile, 0.69 (95% CI: 0.51 ~ 0.92,  = 0.012) in the third quartile, and 0.59 (95% CI: 0.43 ~ 0.82,  = 0.002) in the fourth quartile, respectively. Restricted cubic spline analysis revealed a steady negative linear correlation between CDAI and CFI, with a -value for non-linearity of 0.122. Subgroup analysis did not reveal any significant interactions based on age, education level, family income, history of diabetes, hypertension, stroke, and depression.

Conclusion: CDAI was inversely associated with CFI in a large representative American population. Further longitudinal studies are needed for causal inference.