Age-related memory decline and apolipoprotein E e4.

The APOE epsilon4 allele is associated with risk of late-onset Alzheimer's disease (AD). Longitudinal memory decline in asymptomatic APOE epsilon4 carriers shows greater acceleration compared with non-carriers, with a possible allele-dose effect, and begins prior to age 60. These results correlate with imaging and neuropathological studies that show AD-like changes at this age and collectively support the existence of a presymptomatic stage of AD.