Emerging
magnetic resonance imaging (MRI) research suggests that abdominal fat
in midlife may have a significant impact on cognitive decline.
For the study, recently published in JAMA Network Open,
researchers reviewed brain MRI data, cognitive testing, diet quality
measurements with the Alternative Healthy Eating Index (AHEI)-2010 score
in 512 participants and waist-to-hip ratio (WHR) measurements in 664
participants. The study authors noted that AHEI-2010 scores were
obtained three times over an 11-year period and WHR measurements were
obtained five times over a 21-year period. Cognitive testing and brain
MRI scans were obtained at a mean age of 70, according to the study.
The
researchers found that participants with a higher WHR in midlife
correlated to findings of higher mean diffusivity in 26.4 percent of
white matter in the cingulum and the superior and inferior longitudinal
fasciculus (ILF). Additionally, the study authors noted radial
diffusivity in 23.1 percent of the aforementioned white matter tracts
for those with higher midlife WHR, and lower fractional anisotropy (FA)
in the corticospinal tract, including the cingulum and ILF.
“These
findings are in line with those of cross-sectional studies showing
associations between higher WHR and lower FA in several white matter
tracts, including the corpus callosum and ILF in older adultsand
cingulum in middle-aged adults. The ILF and cingulum are known to be
implicated in Alzheimer disease, and our results suggest that these
tracts may be especially relevant for WHR-related alterations in axonal
and myelin integrity,” wrote lead study author Daria E.A. Jensen, DPhil,
who is affiliated with the Max Planck Institute for Human Cognitive and
Brian Sciences in Leipzig, Germany, and colleagues.
The
study authors found that improvements in AHEI scoring of diet quality
between middle to older age correlated with lower mean diffusivity (MD)
and lower axial diffusivity (AD) as well as higher FA in the
corticospinal tract, frontal aslant tract, and frontal regions.
“We
identified higher FA in widespread tracts (corticospinal tract and
superior thalamic radiation), lower MD in the optic radiation and the
superior parietal lobe, and lower AD in the SLF (superior longitudinal
fasciculus). These regions have been implicated as markers for white
matter microstructural damage in aging and dementia,” pointed out Jensen
and colleagues.
Three Key Takeaways
1. Abdominal fat and white matter integrity. Higher
waist-to-hip ratio (WHR) in midlife is associated with increased white
matter diffusivity and lower fractional anisotropy (FA), particularly in
brain regions linked to cognitive function and Alzheimer’s disease,
suggesting that midlife obesity may contribute to neurodegeneration.
2. Diet quality and brain health.
Improved diet quality, as measured by the Alternative Healthy Eating
Index (AHEI)-2010, may be linked to better white matter microstructure
in aging, highlighting the potential neuroprotective effects of healthy
dietary habits.
3. Early interventions matter. White
matter integrity mediates the relationship between lower WHR in midlife
and better executive function and working memory later in life,
indicating that early metabolic and dietary interventions may help
preserve cognitive health in aging.
White
matter diffusivity also mediated associations between lower WHR in
midlife and improved cognitive aspects such as executive function and
working memory later in one’s life, according to the researchers.
“These
findings may have implications for optimizing the timing of dietary and
metabolic interventions aimed at maintaining brain and cognitive health
during the lifespan,” posited Jensen and colleagues.
(Editor’s note: For related content, see “Skeletal Muscle Loss and Dementia: What Emerging MRI Research Reveals,” “New PET and MRI Research Suggests that Visceral Fat Reduction May Prevent or Delay Alzheimer’s Disease” and “A Closer Look at the New Appropriate Use Criteria for Brain PET: An Interview with Phillip Kuo, MD, Part 2.”)
In
regard to study limitations, the authors conceded possible
self-reporting errors with use of the food frequency questionnaire (FFQ)
and a predominantly male cohort that precluded assessment of
differences between men and women. Additionally, the researchers
acknowledged that study findings with the cohort, largely comprised of
White British adults with high education levels, may not be applicable
to broader populations.
