Apolipoprotein E4 and Alzheimer's disease in São Paulo - Brazil

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Abstract
Several recently published studies showed the existence of an association between the allele ε4 of the apolipoprotein E and Alzheimer's disease (AD) in developed countries. We examined this association in 55 patients with possible or probable AD and 56 elderly controls referred to outpatient clinics at the "Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo" and "Centro de Saúde Escola da Faculdade de Saúde Pública da Universidade de São Paulo". The allele ε4 was significantly more frequent among patients than controls (20.9% vs 8.9%, p=0.038). Thirty-six percent of the cases presented with at least one allele ε4 compared with only 17.9% of the controls (p=0.027). The presence of at least one ε4 allele increased by 2.63 times the risk of subjects being diagnosed as suffering from AD. All three ε4ε4 patients were male and had a pre-senile onset of the disease. There was no significant difference between senile and pre-senile cases (41.9% vs 29.2%, p=0.326) nor between men and women (36.0% vs 36.7%, p=0.959) regarding their risk of being ε4. The age at onset of symptoms did not differ among the different genotype groups, although ε4ε4 cases showed a consistent trend for earlier onset. When only patients with the diagnosis of "probable AD" were included in the analysis (n=43), we observed that 22.1% of the alleles were e4, a rate that was significantly higher than the 8.9% of controls (p=0.024). This study supports the association between the presence of the ε4 allele and AD and extend this finding to Brazilian patients. Nonetheless, the presence of this allele is not necessary nor sufficient for the development of the disease and it is possible that its contribution to the pathogenesis of the disorder depends on the subject's ethnic group.