Dementia, quantitative neuroimaging, and apolipoprotein E genotype

Area of Science:

• Neuroimaging
• Geriatric Medicine
• Genetics

Background:

• Elderly individuals with cognitive disorders, including dementia (Alzheimer's disease, vascular dementia) and mild cognitive impairment, were studied.
• The role of the apolipoprotein E (APOE) epsilon4 allele and cognitive deficit severity on brain structure was investigated.

Purpose of the Study:

• To examine quantitative Magnetic Resonance Imaging (MRI) differences in an elderly population with various clinical disorders.
• To assess potential quantitative MRI differences based on the presence of the APOE epsilon4 allele and the level of cognitive deficit.

Main Methods:

• 180 subjects with dementia or clinical disorders were selected from 5,677 elderly individuals.
• APOE genotype was determined, and brain MRI scans were quantified using a multispectral segmentation algorithm.
• Cognitive status was assessed using a modified Mini-Mental Status Examination, with age and disease duration as covariates.

Main Results:

• Significant brain volume reductions (total brain, hippocampus, gray/white matter) and increased CSF/ventricular volumes were observed in all dementing illnesses.
• Mild cognitive impairment subjects showed fewer atrophic changes but were distinct from controls.
• The APOE epsilon4 allele was linked to smaller hippocampal volume early in Alzheimer's and vascular dementia, but this effect diminished with age and disease duration adjustments.

Conclusions:

• The APOE epsilon4 allele's effect on brain morphology may be subtle and early in dementia development, not significantly affecting later cerebral atrophy.
• Cognitive impairment is associated with brain atrophy regardless of the specific diagnosis or APOE epsilon4 allele presence.