Cortical 11C-PIB Uptake is Associated with Age, APOE Genotype, and Gender in “Healthy Aging”

BACKGROUND/OBJECTIVE: Our aim was to elucidate factors that contribute to amyloid-β (Aβ) accumulation in the brains of the seemingly healthy elderly population, and whether there is interplay between those factors. METHODS: We conducted a cross-sectional positron emission tomography (PET) study with the amyloid tracer 11C-PIB, in 64 cognitively healthy subjects (54-89 years). In addition to PET, magnetic resonance imaging, neuropsychological testing, and APOE genotyping was performed. The results were assessed with a statistical general linear model as well as with Statistical Parametric Mapping (SPM). RESULTS: The effects of age (p < 0.001), APOE ε4 carrier status (p = 0.003), and gender (p = 0.001) on composite cortical 11C-PIB uptake were all significant. The effect of educational level was non-significant (p = 0.37). No significant interactions were found between any of the factors. Cortical 11C-PIB uptake increased, on the average, by 0.015 cortex/cerebellar cortical ratio unit, with every year of age. APOE ε4 positive subjects exhibited higher cortical 11C-PIB uptake than APOE ε4 negative subjects (unadjusted means 1.49 ± 0.34 versus 1.29 ± 0.26) and males had higher uptake than females (1.49 ± 0.39 versus 1.29 ± 0.22), irrespective of age. The results of the voxel-based (SPM) analysis were similar. In addition, SPM analysis showed that lower CERAD score was associated with higher 11C-PIB uptake in the frontal cortex. CONCLUSIONS: Age and APOE ε4 genotype were associated with higher 11C-PIB uptake. In this sample of cognitively healthy elderly individuals, men exhibited higher 11C-PIB uptake than women. Possible gender differences in Aβ accumulation have not been addressed in detail in previous studies, and deeper evaluation in the future is warranted.