Alzheimer’s disease is a degenerative disease of the central nervous system, also known as Alzheimer’s disease, and is the most common type of dementia in old age. It is the most common type of dementia in old age. It usually has an insidious onset and develops chronically and progressively, mainly manifesting as cognitive decline and non-cognitive neuropsychiatric symptoms. As medical research on Alzheimer’s disease continues, it is now believed that there is a pre-dementia stage before the dementia stage, which can be considered as the precursor of Alzheimer’s disease. In this stage, the body has already developed the corresponding pathophysiological changes, but the clinical symptoms have not yet appeared or have only mild clinical symptoms. The pre-dementia stage is further divided into 2 phases, namely the pre-mild cognitive dysfunction and the mild cognitive dysfunction phase. The pre-mild cognitive impairment stage can be a subclinical stage without any clinical manifestations of cognitive impairment or with mild memory loss. Mild cognitive impairment is mainly manifested as mild impairment of memory, mainly near-event forgetfulness, patients often complain of “forgetfulness”, such as not being able to recall recent events or work done, forgetting where to put frequently used items, asking the same question repeatedly, etc. This is often thought of as “forgetfulness” in the elderly and is ignored by the patient and family. The ability to learn new knowledge and accept new things decreases, the attention span decreases, and the language expression also appears to be impaired, the language is repetitive, the words do not make sense; the mood fluctuation is high, easily irritated and easily angry, suspicious, or depressed, anxiety. Other impairments such as visual-spatial skills, executive functions, and abstract thinking may also occur, but they do not affect basic daily living skills and do not reach the level of dementia. Therefore, when an older person in the family has a gradual increase in “forgetfulness”, or inattention, or language impairment, or mood changes, it is important to be alert to the early signs of dementia and seek professional evaluation.