Preclinical memory decline in cognitively normal apolipoprotein E-epsilon4 homozygotes

Area of Science:

• Neuroscience
• Genetics
• Cognitive Aging

Background:

• The apolipoprotein E (apoE)-4 allele is a known risk factor for Alzheimer's disease (AD).
• Positron Emission Tomography (PET) studies indicate reduced cerebral metabolism in cognitively normal apoE-4 carriers, suggesting very early AD pathology preceding clinical symptoms or hippocampal atrophy.

Purpose of the Study:

• To investigate the influence of apolipoprotein E (apoE) genotype on age-related memory decline in non-demented individuals.
• To determine if genetic variations in apoE impact cognitive function in aging.

Main Methods:

• A cross-sectional study involving cognitively normal individuals aged 49-69.
• Participants were categorized into three groups based on apoE genotype: apoE-4 homozygotes (n=25), apoE-4 heterozygotes (n=25), and apoE-4 noncarriers (n=50).
• Neuropsychological tests, including measures of immediate and delayed recall, were administered and compared across genetic groups, controlling for age, gender, and education.

Main Results:

• No significant differences in overall mean scores were observed across the apoE genotype groups.
• However, tests assessing immediate and delayed recall demonstrated a significant negative correlation with age specifically within the apoE-4 homozygote group compared to noncarriers.

Conclusions:

• Cognitively healthy individuals with the apoE-4/4 genotype experience age-related memory decline earlier than those with other apoE genotypes.
• This accelerated memory decline in apoE-4 homozygotes precedes the clinical diagnosis of Alzheimer's disease, aligning with findings in early AD studies.