APP and Alzheimer disease: Considering that the phenotype of sleep disturbances observed in TgCRND8, comprising a NREM sleep deficit, resembles more closely that observed in other multi-transgenic AD mouse models, rather than the early REM sleep deficit observed in the APP transgenic Tg2576 and PDAPP mice, it may be that the severity of neuropathology incurred by the expression of multiple transgenes, rather than the specific transgenes expressed is more closely related to sleep-wake disruption.