New MRI Research Explores Links Between Waist-to-Hip Ratio and Memory in Aging

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.

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.