Alzheimer's disease (AD) is a neurodegenerative disorder and one of the most common forms of dementia. AD has an insidious onset, with clinical manifestations primarily including cognitive impairment, abnormal mental behavior, and decline in social living functions. It is a neurodegenerative disease with progressive progression. According to the patient's condition, AD is typically divided into preclinical stage, mild cognitive impairment (MCI), mild, moderate, and severe AD. Patients are usually in the latter three stages when clinically diagnosed.