Although cerebrospinal fluid levels of hypocretin in DLB and Parkinson’s disease dementia show wide variability, ranging from very low to normal levels [56–58], there is pathologic evidence of greater hypocretin immunoreactive cell loss in DLB compared to AD [59,60], with one DLB study showing hypocretin cell loss correlating with hypersomnolence and α-synuclein [60]. Here, HCRT is linked to Alzheimer disease.