RAG Files/Alzheimer's Disease - Causes - 3.txt

Genetic
Late onset
Late-onset Alzheimer's is about 70% heritable.[48][49] Genetic models in 2020 predict Alzheimer's disease with 90% accuracy.[50] Most cases of Alzheimer's are not familial, and so they are termed sporadic Alzheimer's disease.[medical citation needed] Most cases of sporadic Alzheimer's disease are late onset, developing after the age of 65 years.[51]

The strongest genetic risk factor for sporadic Alzheimer's disease is APOEε4.[14] APOEε4 is one of four alleles of apolipoprotein E (APOE). APOE plays a major role in lipid-binding proteins in lipoprotein particles and the ε4 allele disrupts this function.[52] Between 40 and 80% of people with Alzheimer's disease possess at least one APOEε4 allele.[53] The APOEε4 allele increases the risk of the disease by three times in heterozygotes and by 15 times in homozygotes.[54] Like many human diseases, environmental effects and genetic modifiers result in incomplete penetrance. For example, Nigerian Yoruba people do not show the relationship between dose of APOEε4 and incidence or age-of-onset for Alzheimer's disease seen in other human populations.[55][56]