Excessive daytime sleepiness (EDS) is rather common in the elderly, however, it does not mean that EDS is physiological in that population. EDS may be caused by sleep related breathing disorder (SRBD), which is very popular among elderly people. Also EDS of narcolepsy is a life-long symptom. Recently, many reports come out indicating that EDS would be a predictor of future cognitive decline. One report shows that patients with preclinical Alzheimer disease have significantly higher number of naps per week than controls. EDs may be a harbinger of Alzheimer disease.