ω-3 fatty acids and domain-specific cognitive aging: secondary analyses of data from WHISCA

Abstract

Objective: To test the hypothesis that higher levels of red blood cell (RBC) docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) have a protective association with domain-specific cognitive function in women aged 65 years and older.

Methods: A total of 2,157 women with normal cognition enrolled in a clinical trial of postmenopausal hormone therapy were followed with annual cognitive testing for a median of 5.9 years. In this retrospective cohort study, we assessed the relationship between prerandomization RBC DHA + EPA levels and a) cognitive measures at baseline, and b) cognitive change over time. Endpoints were composite cognitive function and performance in 7 cognitive domains: fine motor speed, verbal memory, visual memory, spatial ability, verbal knowledge, verbal fluency, and working memory.

Results: After adjustment for demographic, clinical, and behavioral characteristics, no significant (p < 0.01) cross-sectional cognitive differences were found between women in the high and low DHA + EPA tertiles at the time of the first annual cognitive battery. In addition, no significant (p < 0.01) differences were found between the high and low DHA + EPA tertiles in the rate of cognitive change over time.

Conclusions: We did not find an association between RBC DHA + EPA levels and age-associated cognitive decline in a cohort of older, dementia-free women.

Figures

Figure 1. Mean baseline cognitive differences between high and low DHA + EPA tertiles with 99% confidence intervals, adjusted for model 1 and model 2 covariates

Model 1: DHA + EPA tertile, DHA + EPA tertile*time interaction, time (linear and quadratic), first test indicator variable, age at first WHISCA examination (linear and quadratic), age*time interaction, HT trial arm, HT trial arm*time interaction, verbal memory test form (for composite cognition and verbal memory outcomes). Model 2: model 1 + education, education*time interaction, race, region, income, body mass index, physical activity, alcohol consumption, smoking, daily caloric intake. DHA = docosahexaenoic acid; EPA = eicosapentaenoic acid; HT = hormone therapy; WHISCA = Women's Health Initiative Study of Cognitive Aging.

Figure 2. Mean differences in cognitive change over time between high and low DHA + EPA tertiles with 99% confidence intervals, adjusted for model 1 and model 2 covariates

Model 1: DHA + EPA tertile, DHA + EPA tertile*time interaction, time (linear and quadratic), first test indicator variable, age at first WHISCA examination (linear and quadratic), age*time interaction, HT trial arm, HT trial arm*time interaction, verbal memory test form (for composite cognition and verbal memory outcomes). Model 2: model 1 + education, education*time interaction, race, region, income, body mass index, physical activity, alcohol consumption, smoking, daily caloric intake. DHA = docosahexaenoic acid; EPA = eicosapentaenoic acid; HT = hormone therapy; WHISCA = Women's Health Initiative Study of Cognitive Aging.