INS and Cognitive impairment: Given that APOE is a key molecule in lipid metabolism that plays an important role in the pathogenesis of cognitive impairment, in the present study, we aimed to explore the potential link between APOE-mediated lipid metabolic regulation and the shared pathological mechanisms of the three categories of cognitive impairment (AD, DCI, and VD), including Aβ protein deposition, tau protein hyperphosphorylation, and insulin resistance.