Frequency of the APOE-4 allele in Alzheimer's disease and its variation with age in Asturias (Spain)

BACKGROUND: Patients with late-onset Alzheimer's disease show a higher freq uency of the APOE-4 than controls. The usefulness of the APOE genotyping in the diagnosis of the disease is controversial. Recently, an age dependent prevalence of APOE-4 in Alzheimer's disease has been described, with a maxi mum frequency for patients with an age at onset between 65 and 80 years. Ad ditionally, the APOE-4 frequency in healthy controls is similar among the d ifferent age-groups, including healthy octogenarians. These data suggest th at APOE-4 determines when and not who will develop the disease. PATIENTS AND METHODS: The APOE genotype was defined following a previously described PCR-protocol. We analysed 120 patients with clinically defined pr obable Alzheimer's disease and 250 controls from the same Caucasian populat ion (Asturias, Northern Spain). RESULTS: We found a significantly higher frequency of the APOE-4 in patient s, compared to controls (p = 0.00001). The prevalence of this allele was 65 % among patients with an age at onset 66-70, falling to 36% and 18% in pati ents younger than 65 and older than 80 years, respectively. The average age (80) at onset did not differ between the E-44 (69 years), E-34 (73 years) and E-33 (73 years). APOE-4 frequency was similar between the different age -groups of controls, including healthy octogenarians. CONCLUSIONS: In Asturias, APOE genotyping can not be used for the presimpto matic diagnosis of Alzheimer's disease. However, individuals carrying this allele would have a higher probability of developing the disease at an age between 65 and 80 years if they am predisposed (genetically and/or environm entally) to the disease.