APOE and Cognitive impairment: Apart from age, the severity of cognitive impairment [15], the ε4 allele of the apolipoprotein E (ApoE) gene [14], hippocampal atrophy [15] and a cerebrospinal fluid (CSF) biomarkers’ profile compatible with AD (i.e., low CSF Aβ42 and high CSF Tau) [15], have also been reported as predictors of progression to AD.