To date, multifactor possible pathophysiological causes have been hypothesized to be at the basis of cognitive impairments and dementia, such as the dopaminergic neuronal loss and the presence of Lewy bodies in cortical and limbic regions, the presence of tau and amyloid pathologies along with the presence of ε4 allele of the Apolipoprotein E (APOE), alterations in other neurotransmitter systems, early synaptic changes, inflammation, and mitochondrial dysfunction [10,14]. Here, APOE is linked to Cognitive impairment.