Isoflavone intake is associated with longitudinal changes in hippocampal volume, but not total grey matter volume, in Japanese middle-aged and older community dwellers.

PURPOSE

This study aimed to clarify the associations between isoflavone intake and the volume changes of brain regions, specifically the hippocampus and total grey matter (TGM), over 10 years in Japanese middle-aged and older community dwellers.

METHODS

Data from the National Institute for Longevity Sciences-Longitudinal Study of Aging of 654 men and 671 women aged 40-85 years at baseline (6th wave survey, 2008-2010) who participated in the follow-up study (9th wave survey, 2018-2022) were analyzed. Total isoflavone intake was estimated based on a 3-day dietary record and categorized into quintile groups. The volumes of the hippocampus and TGM were measured by T1-weighted magnetic resonance imaging and longitudinal FreeSurfer software. Estimated mean brain volume changes by quintile of total isoflavone intake were assessed by a general linear model, with a stratified analysis by age group (< 65/≥65 years).

RESULTS

There were no significant associations between quintile of isoflavone intake and both brain volume changes over 10 years in all participants. On stratification by age group, the multivariable-adjusted difference over time and % change in hippocampal volume were more strongly associated with quintile of total isoflavone intake in those aged ≥ 65 years (difference over time: p for trend = 0.009; % change: p for trend = 0.012). There were no significant longitudinal associations between quintile of total isoflavone intake and TGM volume change in both age groups.

CONCLUSION

In older Japanese people aged ≥ 65 years, increased intake of total isoflavones might be a new nutritional strategy to prevent hippocampal atrophy.