Correlations between APOE4 allele and regional amyloid and tau burdens in cognitively normal older individuals

Background: The correlations between apolipoprotein epsilon 4 (APOE4) status and regional amyloid, tau, and cortical thickness in cognitively normal elderly are not fully understood. Our cross-sectional study aimed to compare regional amyloid/tau burden, and cortical thickness according to APOE4 carrier status and assess correlations between APOE4 and Alzheimer’s disease (AD)-related biomarker burdens. Methods: We analyzed 185 cognitively normal participants from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) cohort. Participants aged 55–90 with normal cognitive function were divided into amyloid ꞵ-positive (Aß+) APOE4 carriers (group 1, n = 27), Aß+ APOE4 non-carriers (group 2, n = 29), and Aß- normal controls (group 0, n = 129). We compared amyloid depositions, tau depositions, and cortical thickness among the 3 groups and assessed correlations between APOE4 existence and imaging biomarkers adjusted for age and sex. Results: The participants in group 2 were older than those in the other groups. The regional amyloid/tau standardized uptake value ratios (SUVRs) did not differ between groups 1 and 2, but the amyloid/tau SUVRs in most regions were numerically higher (especially in the younger (< 70) participants) in group 1 than group 2 after adjusting for age difference. APOE4 allele had robust correlations with increased amyloid burden in the fronto-temporo-parietal cortical areas after adjustment for age and sex, but it had weaker and mixed correlations with the regional tau burden and did not have significant correlation with cortical thickness. Conclusions: We identified that the presence of APOE4 allele might be more highly associated with amyloid deposition than with other AD-related biomarkers such as tau or cortical thickness, especially in the younger group below 70 in cognitively normal elderly.