March 27, 2025 from Medscape
Maintaining a nutritious diet and a lower waist-to-hip ratio (WHR) between the ages of 48 and 70 may be key to better brain function in older age, according to new research from the University of Oxford and University College London.
The study, published in JAMA Network Open, used data from the longstanding Whitehall II cohort. Researchers tracked diet quality, WHR, and later-life brain imaging and cognitive performance to uncover how midlife lifestyle choices may influence aging brains.
Tracking Diet and Waist-to-Hip Ratio Over Time
In total, 512 participants were included in the diet portion of the study and 664 in the WHR analysis. Most participants were men in their late 40s at baseline. Researchers assessed diet quality using the Alternative Healthy Eating Index (AHEI-2010) at three points over 11 years, and measured WHR five times over 21 years.
By age 70, participants underwent diffusion tensor imaging and resting-state fMRI to examine white matter integrity and hippocampal connectivity. Cognitive function was also assessed through verbal memory, semantic fluency, and digit span tests.
Better Diet, Better Brain Connections
A healthier diet in midlife was linked to enhanced brain connectivity. The left hippocampus — critical for memory — showed stronger links to areas like the occipital lobe and cerebellum among those with higher AHEI-2010 scores. Specifically, the left hippocampus had a volume of 9176 mm³ and stronger functional connectivity with the right cerebellum (136 mm³), both statistically significant findings.
These brain regions play a key role in memory consolidation and coordination, hinting that good nutrition may support functional brain networks well into old age.
Higher Waist Size, Lower Cognitive Scores
In contrast, a higher WHR during midlife was associated with lower cognitive scores and poorer white matter structure. Increased WHR correlated with greater mean and radial diffusivity in white matter — a sign of reduced integrity — affecting up to 26% of white matter tracts.
Participants with larger WHRs performed worse on verbal episodic memory, digit span, and semantic fluency tests. White matter changes partly explained the link between WHR and cognitive performance.
Midlife Is a Window for Prevention
The study authors noted that
“these findings suggest that interventions to improve diet and manage central obesity might be best targeted in midlife to obtain beneficial outcomes for brain and cognitive health in older age,”
In an editorial accompanying the study, Dr. Sharmili Edwin Thanarajah of University Hospital Frankfurt emphasized that many cases of dementia may be preventable through better midlife health. She stated that the research has “important implications for prevention strategies,”particularly in improving metabolic health through lifestyle change.
Study Limitations to Consider
The researchers acknowledged several limitations. Diet was self-reported using a food frequency questionnaire, which may not capture all habits accurately. Most participants were White, highly educated British men, which may limit the applicability of the findings to broader populations.
Still, the study adds weight to a growing body of evidence: taking care of your health in your 40s and 50s may pay off with better brain function decades later.
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