APOE genotype and early β-amyloid accumulation in older adults without dementia

To clarify associations between APOE ε4 allele and age on longitudinal rates of β-amyloid (Aβ) accumulation within Aβ+ and Aβ- older individuals without dementia.We analyzed 595 older adults without dementia classified cross-sectionally as Aβ- (n = 325) and Aβ+ (n = 270) using longitudinal florbetapir PET. The influence of age and APOE genotype on longitudinal accumulation of Aβ was examined with linear mixed models.APOE ε4 and older age were associated with higher risk of being classified as Aβ+ at baseline. The annual rate of Aβ accumulation was significantly greater than zero for Aβ- ε3 (0.0021 ± 0.0007 standardized uptake value ratio [SUVR] units) and Aβ- ε4 (0.0044 ± 0.0010 SUVR units), as well as Aβ+ ε3 (0.0141 ± 0.0019 SUVR units) and Aβ+ ε4 (0.0126 ± 0.0018 SUVR units). Aβ accumulation was significantly faster in Aβ- ε4 compared to Aβ- ε3 and Aβ- ε2. Rates of Aβ accumulation did not differ significantly between Aβ+ APOE groups. Older age was associated with higher rates of Aβ accumulation in the Aβ- group.APOE ε4 carriage and older age were predictors of longitudinal Aβ accumulation within the Aβ- group but not the Aβ+ group. APOE ε2 carriage was protective against longitudinal Aβ accumulation within the Aβ- group. APOE genotype in conjunction with chronologic age may aid in participant selection for primary prevention trials aimed at halting Aβ accumulation before abnormal levels are reached.