APOE variants and Alzheimer's disease risk factors

From Wikipedia:

"Although 40–65% of Alzheimer's disease (AD) patients have at least one copy of the ε4 allele, ApoE4 is not a determinant of the disease – at least a third of patients with AD are ApoE4 negative and some ApoE4 homozygotes never develop the disease.

Yet those with two ε4 alleles have up to 20 times the risk of developing AD. There is also evidence that the ApoE2 allele may serve a protective role in AD. Thus, the genotype most at risk for Alzheimer's disease and at an earlier age is ApoE 4,4.

Using genotype ApoE 3,3 as a benchmark (with the persons who have this genotype regarded as having a risk level of 1.0), individuals with genotype ApoE 4,4 have an odds ratio of 14.9 of developing Alzheimer's disease.

Individuals with the ApoE 3,4 genotype face an odds ratio of 3.2, and people with a copy of the 2 allele and the 4 allele (ApoE 2,4), have an odds ratio of 2.6.

Persons with one copy each of the 2 allele and the 3 allele (ApoE 2,3) have an odds ratio of 0.6. Persons with two copies of the 2 allele (ApoE2,2) also have an odds ratio of 0.6."

Two significant loci for APOE: SNP variants

Homozygous coding - as normally presented.

I'm 3,3 and Clare's 3,4.

Here's the incidence.

"Age is the most important risk factor for AD, with the prevalence rising substantially between the ages of 65 and 85 years.

The incidence of the disease doubles every five years after 65 years of age, with diagnosis of 1275 new cases per year per 100,000 persons older than 65 years, so that AD affects 30%–50% of all people by the age of 85 years.

Data on centenarians show that AD is not necessarily the outcome of aging, but the odds of receiving a diagnosis of AD after 85 years exceed one in three."