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.