Data were derived from the National Institute for Longevity Sciences-Longitudinal Study of Aging. Subjects comprised 403 men and 373 women aged 60–81 years at baseline who participated in the follow-up study at least once. Bean, soy product and soy isoflavone intake was assessed using a 3-day dietary record at baseline. Cognitive function was assessed by the Mini-Mental State Examination (MMSE). MMSE scores of ≤23 were used to define cognitive impairment. The relationship between bean, soy product and soy isoflavone intake and cognitive impairment was assessed using a generalized estimating equation. Multivariate-adjusted odds ratios (95% confidence intervals) for cognitive impairment with a 1 s.d. increase in total bean, total soybean and total soy isoflavone intakes were 0.48 (0.28–0.81; p = 0.006), 0.51 (0.32–0.83; p = 0.007), and 0.55 (0.32–0.93; p = 0.026), respectively, in women. Total soybean and soy isoflavone intake might decrease the risk of cognitive impairment in elderly Japanese women.
We obtained written informed consent for study participation from each participant. The study protocol was reviewed and approved by the Committees of Ethics of Human Research of the National Center for Geriatrics and Gerontology. The authors thank the study participants and our colleagues in the NILS-LSA for completing the survey for this study.Author contributions
All the authors (MN, RO, YN, CT, MT, YK, TI, TS, FA and HS) developed the idea for this study. RO, YN, CT, MT, YK, TI, FA, and HS collected the data. Measurements and data analysis was completed by MN. FA and HS provided medical advice regarding interpretation of the data. MN drafted the manuscript with the help of RO. All authors read and approved the final version of the manuscript.