Education and occupation provide reserve in both ApoE ε4 carrier and noncarrier patients with probable Alzheimer's disease

According to the reserve hypothesis, a high educational/occupational attainment can modulate Alzheimer's disease (AD) clinical expression. The impact of the Apolipoprotein E (ApoE) epsilon 4 allele on the reserve mechanism in AD has not been assessed. Aim of this European multicenter study was to evaluate the metabolic correlates of reserve and ApoE genotype in early probable AD. 51 AD subjects, 27 epsilon 4 carriers, and 24 noncarriers, underwent FDG-PET brain imaging. We used the general linear model as implemented in SPM2 to test for the linear correlation of a reserve index, accounting for both educational and occupational level, with brain glucose metabolism, controlling for demographic variables (age and gender) and for cognitive performance. We found an inverse correlation between a reserve index, accounting for educational/occupational level, and metabolism in the posterior cingulate cortex and precuneus in both epsilon 4 carriers and noncarriers, and no significant difference between the groups. We show that education and occupation act as proxies for reserve in epsilon 4 carriers, compensating for an unfavorable genetic background; we also show that the degree of compensation does not differ significantly by ApoE epsilon 4 status.