A patient's inheritance of alleles for apolipoprotein E (APOE) affects his or her risk of developing Alzheimer's disease (AD).
APOE alleles (designated "epsilon") are on chromosome 19:
(1) epsilon 2
(2) epsilon 3
(3) epsilon 4
The allelic dose of epsilon 4 determines the risk for Alzheimer's disease. Approximately 40% of Alzheimer's cases have been linked to the APOE genotype (Martin, 1999).
Impact: on senile dementia (onset after age 60), not early onset
Influences:
(1) hazard ratio for developing Alzheimer's disease
(2) age of onset
Number of Epsilon 4 Alleles |
Odds Ratio (Tsai) |
Odds Ratio (Corder) |
0 |
1 |
1 |
1 |
4.4 |
2.8 |
2 |
19.3 |
8 |
where:
• The odds ratios for 2 alleles = (odds ratio for 1 allele) * (odds ratio for 1 allele)
Number of Epsilon 4 Alleles |
Median Age of AD Onset (Tsai) |
Median Age of AD Onset (Corder) |
0 |
74 years |
67 years |
1 |
78 years |
74 years |
2 |
83 years |
88 years |
Specialty: Neurology