Figure 1. The figure shows the theoretical antagonistic pleotropic (AP) effect of APOE gene across the entire human lifespan. The increased probability of early survival and normal cognition later in life are alternatively correlated with the presence of APOE4 and APOE2 allele. However, other genes and environmental factors through their mutual interactions from the in-utero life until centenarian age can probably potentiate the beneficial or detrimental effects on the onset and manifestations of brain diseases and, respectively, reduce or potentiate the genetic predisposition toward more negative or positive clinical outcomes during different periods of life.