The L-shaped Relationship Between Composite Dietary Antioxidant Index and Cognitive Impairment in the American Elderly: A Cross-Sectional Study (NHANES 2011-2014)

Background Oxidative stress is involved in the development and progression of cognitive impairment. However, the association between composite dietary antioxidant index (CDAI) and cognitive impairment remains unknown. Objective This cross-sectional study investigated the non-linear relationship between CDAI and cognitive impairment among the American elderly. Methods The public data was available from the United States National Health and Nutrition Examination Survey from 2011 to 2014. Participants aged ≥ 60 years were eligible for cognitive function, including word learning and recall modules from the Consortium to Establish a Registry for Alzheimer’s Disease (CERAD), the animal fluency test (AFT), and the digit symbol substitution test (DSST). A composite cognition score was created to evaluate global cognition. The univariate and multivariate logistic regression analysis, restricted cubic spline, stratified and sensitivity analysis were conducted. Results CDAI was negatively associated with cognitive impairment. For each standard deviation increase in CDAI, the risk of cognitive impairment decreased by 6% for DSST (OR = 0.94, 95% CI: 0.9, 0.97), 7% for AFT (OR = 0.93, 95% CI: 0.9, 0.96), 4% for CERAD (OR = 0.96, 95% CI: 0.93, 0.99), and 7% for global cognition (OR = 0.93, 95% CI: 0.9, 0.96) after adjusting for multiple potential confounders. This significant negative relationship remained consistent when comparing individuals in the highest CDAI tertile with those in the lowest CDAI tertile. Furthermore, a non-linear relationship was observed between CDAI and cognitive impairment on AFT (P for non-linearity = 0.009) and global cognition (P for non-linearity = 0.006).These negative correlations between CDAI and cognitive impairment were observed across the stratified age, gender, poverty-to-income ratio, body mass index, hypertension, and diabetes. However, the interaction test revealed significance for education on DSST (P for interaction = 0.04). Moreover, vitamin E, zinc, selenium, and carotenoids were independently associated with cognitive impairment in this study. The sensitivity analysis for participants with complete covariates yielded a similar finding. Conclusion These findings suggested a negative and L-shaped association between the CDAI and the risk of cognitive impairment among the American elderly. The results have significant implications for public health initiatives to prevent and limit the progression of cognitive impairment through dietary interventions.