However, it is demonstrated recently that the level of orexin-A in cerebrospinal fluid is higher in Alzheimer's disease patients which is positively associated with Alzheimer's disease biomarkers including Aβ and Tau (Liguori et al., 2016; Osorio et al., 2016; Gabelle et al., 2017). This evidence concerns the gene HCRT and Alzheimer disease.