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Association between apolipoprotein E polymorphism and Alzheimer disease in Tehran, Iran
Asad Vaisi Raygani1, Mahine Zahrai, Akbar Vaisi Raygani
1Department of Medical Biochemistry, University of Tehran, Tehran, Iran. vaisiraygani@yahoo.com
Neuroscience Letters
|January 25, 2005
Summary
The apolipoprotein E epsilon 4 (APOE-epsilon4) allele significantly increases Alzheimer's disease risk in Tehran, Iran. This risk is dose- and age-dependent, with APOE-epsilon4 carriers showing earlier disease onset.
Area of Science:
- Neuroscience
- Genetics
- Epidemiology
Background:
- The apolipoprotein E epsilon 4 (APOE-epsilon4) allele is a known major risk factor for Alzheimer's disease (AD).
- The association between APOE allele frequencies and AD risk in developing countries remains largely uncharacterized.
- Understanding regional variations in APOE allele frequencies is crucial for assessing AD risk in diverse populations.
Purpose of the Study:
- To investigate the frequency of apolipoprotein E (APOE) alleles in an Iranian population with Alzheimer's disease (AD) compared to cognitively normal individuals.
- To determine the association between APOE allele variants (epsilon4 and epsilon2) and AD risk, age-at-onset, and dose-dependency in the Tehran population.
- To compare observed APOE genotype frequencies with those reported in other ethnic and geographical groups.
Main Methods:
- Case-control study involving 105 patients with AD and 129 cognitively normal controls from Tehran, Iran.
- Analysis of apolipoprotein E (APOE) allele frequencies, including epsilon4 and epsilon2 variants.
- Statistical analysis to determine odds ratios (OR) for AD risk associated with APOE genotypes, considering age and allele dose.
Main Results:
- APOE-epsilon4 allele frequency was significantly higher in AD patients (21%) compared to controls (6.2%) (p < 0.001).
- APOE-epsilon4 carriers had a substantially increased odds ratio for AD (heterozygous: 3.2, homozygous: 12.75), with a dose- and age-dependent effect.
- AD patients with one or two APOE-epsilon4 alleles exhibited an earlier age-at-onset (p < 0.001).
- APOE-epsilon2 allele frequency was lower in AD patients (0.95%) than controls (2.7%) (p = 0.15) and was not associated with AD onset (OR = 0.34).
- Observed genotype frequencies in controls were similar to those in Turkish, Greek, Japanese, Spanish, and Moroccan populations, but differed from other ethnic groups.
Conclusions:
- The APOE-epsilon4 allele is a significant risk factor for Alzheimer's disease in the Tehran population, demonstrating a dose- and age-dependent relationship.
- The findings highlight the importance of geographical location and ethnic background in the study of APOE genotypes and their association with AD.
- APOE-epsilon2 does not appear to be associated with AD risk in this Iranian cohort.