Total antioxidant capacity of diet in relation to cognitive function and decline.

BACKGROUND: Epidemiologic evidence on the association of individual antioxidant vitamins and cognition is inconsistent.
OBJECTIVE: We evaluated the total antioxidant capacity of diets on the basis of the ferric-reducing antioxidant power (FRAP) assay in relation to cognition in older women.
DESIGN: Starting in 1995, we used a telephone-based cognitive assessment to evaluate cognitive function on 3 occasions at 2-y intervals in 16,010 participants aged ≥70 y in the Nurses' Health Study. In 1980, and every 4 y thereafter, we collected dietary information by using a semiquantitative food-frequency questionnaire (FFQ). For each participant, we combined FFQ data with food- and supplement-specific FRAP values to obtain FRAP scores; these data were averaged from 1980 until the initial cognitive interview to reflect long-term diets. We used multivariable-adjusted linear regression to estimate mean differences in initial cognitive function and slopes of decline across quintiles of FRAP scores.
RESULTS: In multivariable-adjusted models, there was an association between higher total FRAP scores and better cognitive function at the first interview (P for trend = 0.003 for global scores with all cognitive tests combined; mean difference = 0.04 standard units; 95% CI: 0.01, 0.08 standard units, comparing the highest and lowest quintiles). A weaker association was observed for dietary FRAP scores (excluding supplements) and initial global scores (P for trend = 0.05). However, prospective analyses of cognitive decline indicated no associations with total or dietary FRAP scores in models adjusted for multiple potential confounders (P for trend = 0.3 and 0.5 for global scores, respectively).
CONCLUSION: We observed no clear evidence of a consistent association between the total antioxidant capacity of diets and cognition in this cohort of older women.