HCRT and Alzheimer disease: Although in vivo studies have documented an increase in CSF orexin-A levels in patients with MCI and AD [9–11], undisputed evidence has not yet been achieved, and existing studies present conflicting results, since some of them are post-mortem studies and other reports included different other neurocognitive disorders not homogeneously classified according to the last published diagnostic criteria [12–14, 19].