Effect of APOE and CD33 on Cognitive Decline

Area of Science:

• Neuroscience
• Genetics
• Gerontology

Background:

• Alzheimer's disease (AD) diagnosis follows a prolonged period of cognitive decline.
• Individuals with APOE ε4 alleles and a family history of AD show increased cognitive decline risk.
• This study investigates if AD risk genes, combined with APOE, contribute to this heightened risk.

Purpose of the Study:

• To examine the combined effect of APOE ε4 and a genetic risk score (g-score) on cognitive decline.
• To identify specific gene-APOE interactions influencing cognitive trajectories in older adults.
• To understand the genetic underpinnings of Alzheimer's disease risk.

Main Methods:

• Analysis of 7451 participants (aged 65+) from the Health and Retirement Study (HRS) with DNA and cognitive data.
• Calculation of a genetic risk score (g-score) based on established AD risk genes.
• Modeling cognitive function trajectories in four groups based on APOE ε4 status and g-score (low/high).

Main Results:

• The APOE ε4+/high g-score group showed the most significant cognitive decline (p<.0001).
• The combined risk in this group exceeded the additive effects of APOE ε4 or high g-score alone.
• A significant interaction between APOE and the CD33 gene was observed (p=0.04), though not after multiple comparison adjustment.

Conclusions:

• Multiple AD risk genes amplify cognitive decline risk in APOE ε4 carriers.
• The CD33 gene variant may further increase cognitive decline risk in individuals with APOE ε4.
• This highlights the complex interplay of genetic factors in Alzheimer's disease pathogenesis.