Though mid-life obesity is a known risk factor for dementia, how obesity in late life impacts brain health is not well understood, especially in the presence of comorbid risk factors like hypertension (HTN) and impaired glucose tolerance (IGT).
Objective
We investigated associations between obesity, neuroimaging measures, and cognition in middle aged and older adults, specifically testing whether higher body mass index (BMI), waist circumference (WC), and waist-to-hip ratio are associated with brain health independent of HTN and IGT.
Methods
A total of 599 participants with brain MRI, cognitive testing, and anthropometric measurements were examined. Chi square and one-way ANOVA tests were performed to compare participant characteristics across BMI categories. Linear regression models assessed relationships between anthropometric, neuroimaging, and cognitive outcomes with and without adjustment for relevant covariates. We also explored interactions between anthropometric measures and APOE ε4 status and cognitive status.
Results
Higher BMI was associated with higher cerebral blood flow (CBF) in both white matter (β = 0.2294 ± 0.0431, p < 0.001) and gray matter (β = 0.0872 ± 0.0405, p = 0.032), higher free water (β = 0.0906 ± 0.0425, p = 0.034), lower fractional anisotropy (β = -0.0891 ± 0.0433, p = 0.040), and better global cognition (β = 0.022 ± 0.007, p = 0.002) and cognitive composite scores (ps < 0.01), independent of IGT and HTN. Similar associations were observed for waist circumference. Evidence of effect modification by APOE ε4 carrier status and cognitive status were found for white matter CBF, white matter hyperintensities, fractional anisotropy, and cognition.
Conclusions
Obesity measures are positively associated with better brain structure, function, and cognition in aging adults, highlighting the importance of managing body weight in older age to maintain optimal brain health.
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