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

Several recently published studies showed the existence of an association between the allele epsilon 4 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 epsilon 4 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 epsilon 4 compared with only 17.9% of the controls (p = 0.027). The presence of at least one epsilon 4 allele increased by 2.63 times the risk of subjects being diagnosed as suffering from AD. All three epsilon 4 epsilon 4 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 epsilon 4. The age at onset of symptoms did not differ among the different genotype groups, although epsilon 4 epsilon 4 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 epsilon 4, 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 epsilon 4 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.