HAI Book 2025 - Flipbook - Page 168
Callow, Daniel
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Amyloid status moderates associations between hippocampal
microstructure, PET tau burden, and memory in dementia-free older adults
Daniel Callow1, Nisha Rani1, Kylie Alm1, Corinne Pettigrew2, Anja Soldan2, Michael Miller3,
Marilyn Albert2, Arnold Bakker1,2
1
Johns Hopkins School of Medicine Department of Psychiatry and Behavioral Sciences, Baltimore, MD, US
Johns Hopkins School of Medicine Department of Neurology, Baltimore, MD, US
3
Johns Hopkins University Department of Biomedical Engineering, Baltimore, MD, US
2
Growing evidence suggests that hippocampal gray matter microstructure, assessed through diffusion-weighted
imaging (DWI), is a sensitive marker of neurodegeneration in Alzheimer's disease (AD). While hippocampal atrophy
is a characteristic feature of AD, microstructural changes may precede tissue atrophy, offering important insights
into the early phases of disease. This study assessed the relationships between hippocampal microstructure
(assessed with DWI) tau pathology [by positron emission tomography (PET)], and episodic memory performance,
focusing on the moderating role of A´ status assessed by PET imaging. The study included 192 participants
without dementia (14 with mild cognitive impairment [MCI]) from the BIOCARD cohort (mean age = 68), of which 52
(27%) were A´ positive. Multiple linear regression analyses tested whether A´ status moderated associations
between hippocampal mean diffusivity (MD), Braak-staged tau accumulation on PET, and an episodic memory
composite score. Results showed that A´ significantly moderated the associations between higher hippocampal
MD and poorer episodic memory (´ = -0.24, SE = 0.12, p = 0.039), and greater tau accumulation (´ = .29, SE = .08, p
