Isoflavone-Rich Soy Protein and Cognition in Midlife and Late-Life Women: Randomized, Double-Blind, Placebo-Controlled Trial (P04.196)

Abstract

Objective: To determine cognitive effects of long-term dietary soy isoflavones in a daily dose comparable to that of traditional Asian diets. Background Soy isoflavone therapy is suggested to benefit cognitive health in postmenopausal women, but evidence from adequately powered clinical trials is lacking regarding effect on long-term cognitive functioning. Design/Methods: In the parallel-group randomized double-blind Women9s Isoflavone Soy Health (WISH) trial, healthy postmenopausal women were randomly allocated to receive daily 25 g isoflavone-rich soy protein (91 mg aglycone weight of isoflavones) or milk protein matched placebo (0 mg isoflavones). The primary cognitive endpoint compared between groups at 2.5 years was change from baseline on global cognition, a composite score constructed as the weighted sum of 14 individual test score changes from a comprehensive neuropsychological battery. Results: 350 women (mean age 61 years) enrolled in the WISH trial. 313 women with baseline and endpoint cognitive test data were included in intent-to-treat analyses. Adherence in both groups was nearly 90%. There was no significant between-group difference on change from baseline in global cognition (mean standardized improvement of 0.42 in the isoflavone group and 0.31 in the placebo group; mean standardized difference 0.11, 95% CI -0.13 to 0.35). Secondary analyses indicated greater improvement on a visual episodic memory factor in the isoflavone group (mean standardized difference 0.33, 95% CI 0.05 to 0.60) but no significant between-group differences on three other cognitive factors or differences on individual test scores; there was no significant between-group difference within a subgroup of younger postmenopausal women close to menopause. Conclusions: Long-term daily dietary soy isoflavone supplementation has no effect on global cognition among healthy postmenopausal women but may improve visual episodic memory. (ClinicalTrials.gov NCT00118846). Supported by: National Center of Complementary and Alternative Medicine, the Office of Dietary Supplements, and the Office of Research on Women9s Health (U01AT-001653). Disclosure: Dr. Henderson has received research support from Cambridge University Press. Dr. St. John has nothing to disclose. Dr. Hodis has nothing to disclose. Dr. Kono has nothing to disclose. Dr. McCleary has nothing to disclose. Dr. Franke has nothing to disclose. Dr. Mack has nothing to disclose.