The apolipoprotein E epsilon 2 allele and decline in episodic memory

Area of Science:

• Neuroscience
• Genetics
• Cognitive Aging

Background:

• The apolipoprotein E (apoE) epsilon 4 allele is associated with cognitive decline, particularly in episodic memory.
• The impact of the apoE epsilon 2 allele on cognitive function has been less clear.

Purpose of the Study:

• To investigate the effect of apoE genotype on cognitive change over time in older adults.
• To determine if the apoE epsilon 2 allele influences the rate of decline in various cognitive domains.

Main Methods:

• Longitudinal study of 669 cognitively healthy older adults (Religious Orders Study) over eight years.
• Cognitive function assessed annually, with summary measures for episodic memory, semantic memory, working memory, perceptual speed, and visuospatial ability.
• Growth curve models analyzed cognitive change in relation to apoE genotype (epsilon 2, epsilon 3/3 reference, epsilon 4).

Main Results:

• Significant differences in episodic memory change rates among apoE subgroups.
• The apoE epsilon 2 subgroup showed an average annual increase in episodic memory, while epsilon 3/3 and epsilon 4 subgroups declined.
• The apoE epsilon 4 subgroup exhibited faster decline in semantic memory and perceptual speed compared to epsilon 3/3.

Conclusions:

• Presence of one or more apoE epsilon 2 alleles is linked to slower decline in episodic memory in older individuals.
• The apoE epsilon 2 allele does not appear to affect the rate of decline in other cognitive domains.
• Findings highlight differential effects of apoE alleles on cognitive aging trajectories.