The most common form of Aβ produced by APP ends at amino acid position 40 (Aβ40, ~80–90%), whereas Aβ ending at position 42 (Aβ42, ~5–10%) has greater neurotoxicity and is thought to have a preferential role in the formation of AD-related amyloid plaques13 AD amyloid plaques are formed from aggregated extracellular fibrils of Aβ and have been associated with cognitive impairment and dementia. This evidence concerns the gene APP and Alzheimer disease.