Abstract
Background
The apolipoprotein E (APOE) ε4 allele is a major genetic risk factor for late-onset Alzheimer’s disease (AD), yet there is little consensus about how and when the allele exerts its influence on the brain.
Methods
In this scoping review, we synthesized research examining APOE ε4-related differences on MRI-derived measures of brain structure, function, and connectivity in cognitively unimpaired, middle-aged adults (aged 40–65 years). Four online databases (Ovid MEDLINE, Ovid Embase, Ovid PsycINFO, Scopus) were searched on July 11, 2024, and forward/backward reference searching was conducted on identified studies. We extracted data on sample characteristics, methods, and key APOE ε4-related results.
Results
Our pre-registered search strategy identified 30 relevant studies. Overall, we found little evidence of robust, consistent differences between APOE ε4 carriers and non-carriers at midlife, especially in relation to brain structure. However, among the studies identified, small samples were common, and limited consideration was afforded to factors such as sex and ethnocultural diversity.
Conclusion
Overall, the existing literature indicates that APOE ε4 exerts little, if any, influence on brain structure at midlife, while differences in brain function and connectivity remain poorly characterized.
The apolipoprotein E (APOE) ε4 allele is a major genetic risk factor for late-onset Alzheimer’s disease (AD), yet there is little consensus about how and when the allele exerts its influence on the brain.
Methods
In this scoping review, we synthesized research examining APOE ε4-related differences on MRI-derived measures of brain structure, function, and connectivity in cognitively unimpaired, middle-aged adults (aged 40–65 years). Four online databases (Ovid MEDLINE, Ovid Embase, Ovid PsycINFO, Scopus) were searched on July 11, 2024, and forward/backward reference searching was conducted on identified studies. We extracted data on sample characteristics, methods, and key APOE ε4-related results.
Results
Our pre-registered search strategy identified 30 relevant studies. Overall, we found little evidence of robust, consistent differences between APOE ε4 carriers and non-carriers at midlife, especially in relation to brain structure. However, among the studies identified, small samples were common, and limited consideration was afforded to factors such as sex and ethnocultural diversity.
Conclusion
Overall, the existing literature indicates that APOE ε4 exerts little, if any, influence on brain structure at midlife, while differences in brain function and connectivity remain poorly characterized.
| Original language | English |
|---|---|
| Article number | 100364 |
| Journal | The Journal of Prevention of Alzheimer's Disease |
| Volume | 12 |
| Issue number | 9 |
| DOIs | |
| Publication status | Published - 2025 |
Keywords
- Apolipoprotein E
- Midlife
- Brain structure
- Brain function
- Structural connectivity
- Functional connectivity