Dementia in the elderly, mainly referring to Alzheimer's disease, is primarily characterized by a significant decline in the patient's memory and learning abilities. Of course, there are some prodromal symptoms before the onset of dementia. For example, patients might show no clinical signs of cognitive impairment or only display very slight memory decline. Patients might exhibit mild impairment in memory, a decrease in the ability to learn and retain new information, and mild impairments in other cognitive areas such as attention, executive function, language skills, and visuospatial abilities. However, these impairments are very slight and can go unnoticed by family members. Moreover, these mild impairments do not affect the patient's basic daily life abilities and do not reach the level of dementia. Patients can live independently and manage their routine daily tasks, which are mainly some of the early signs of dementia.