Lim YY, et al. - This study was performed to elucidate relationships between APOE ε4 allele and age on longitudinal rates of β-amyloid (Aβ) accumulation within Aβ+ and Aβ- older individuals without dementia. Within the Aβ- group, APOE ε4 carriage, and older age were predictors of longitudinal Aβ accumulation but not the Aβ+ group. Within the Aβ- group, APOE ε2 carriage was protective against longitudinal Aβ accumulation. APOE genotype in conjunction with chronologic age could aid in participant selection for primary prevention trials aimed at halting Aβ accumulation before abnormal levels were reached.