However, considering that such changes have also been found in diagnosed and at-risk AD patients with APOE4 (Drzezga et al., 2005; Lind et al., 2006; Trivedi et al., 2006; Xu et al., 2009; Liu et al., 2010; Spampinato et al., 2011; Canuet et al., 2012; Ossenkoppele et al., 2013; Wesnes et al., 2014; Wang et al., 2015; Mirza et al., 2019; Abushakra et al., 2020), it is plausible to hypothesize that APOE4 contributes to these brain pathologies in PD and DLB through mechanisms implicated in AD pathogenesis, overall leading to cognitive impairment. This evidence concerns the gene APOE and Cognitive impairment.