Two studies indicate that young people carrying the “Alzheimer’s gene” (ApoE4) do not have the pathological changes found later in life. The first study, involving 1412 adolescents, found no differences in hippocampal volume or asymmetry as a function of gene status. The second study, involving 173 young adults (average age, 28 ± 7.6 years), found no difference in plasma concentrations of amyloid-beta peptides.
http://www.eurekalert.org/pub_releases/2014-04/ip-neo040614.php