Hippocampal Subfield Volumes in Middle-Aged Adults at Risk of Dementia.

Background: Alzheimer's disease (AD) begins decades before the onset of dementia. There is a need to investigate biomarkers of early AD for use in clinical trials and to facilitate early intervention.

Objective: We aimed to determine whether changes in hippocampal subfield volumes in healthy middle-aged adults were associated with risk of future dementia.

Methods: We included 150 participants from the PREVENT-Dementia cohort, which recruited subjects aged 40-59 with or without a family history of dementia (FHD; included here were 81 with FHD and 69 without). Hippocampal subfield volumes were segmented from high resolution T2-weighted 3T MRI images taken at baseline and 2-year follow-up.

Results: FHD and greater 20 year-risk of dementia due to cardiovascular risk factors were both associated with lower CA1 volume. FHD was also associated with a relative increase in combined CA3, CA4, and dentate gyrus volume between baseline and follow-up.

Conclusion: CA1 atrophy may commence as early as middle-age in those with a high risk of future dementia, while increases in CA3, CA4, and dentate gyrus volume may be a response to early AD in the form of inflammation or neurogenesis.