In the early 1990s, many media reported that former U.S. President Reagan suffered from “Alzheimer’s Disease”, and it was through this news that many people first heard of the term “Alzheimer’s Disease”. So what is Alzheimer’s disease? In fact, early senile dementia is an outdated name, now the international common name for Alzheimer’s disease, also known as Alzheimer’s disease, is in the middle and old age onset of disease, with progressive aggravation of memory and intellectual impairment as the main manifestation of the disease. The disease that starts before the age of 65 is generally called pre-senile dementia or early senile dementia, while the disease that starts after the age of 65 is called senile dementia or Alzheimer’s disease. Since Reagan’s disease began after age 65, it is clear that he suffered from Alzheimer’s rather than Progeria. Alzheimer’s disease is the most common type of dementia in old age. Foreign literature reports that the prevalence of Alzheimer’s disease is about 3% in people between the ages of 65 and 74, while the prevalence of Alzheimer’s disease is nearly 50% in people over the age of 85. In addition to this type of dementia, other types of dementia, such as cerebrovascular disease dementia, may develop in old age. Domestic surveys have found that the prevalence of various types of dementia in the population over 60 years of age ranges from 1.38 to 5.99%. Modern psychiatry considers Alzheimer’s disease to be a progressive developmental brain degenerative disease, which is mainly characterized by progressive loss of memory and intelligence. The onset of the disease is very insidious, and the early symptoms of dementia, such as memory loss and intellectual decline, appear without the patient’s knowledge, so the family members are often unable to determine the exact onset time of the patient’s disease. Moreover, because many family members of patients generally believe that the patient’s forgetfulness is a common feature of normal elderly people, and ignore the time of the emergence of these symptoms. The first and only sign of Alzheimer’s disease is memory loss, especially in the recent past. This is when the patient appears to be more forgetful than the average older person, often having difficulty remembering the names of recent events, activities, or familiar people or things, as well as completing simple mathematical thinking and calculations. At this stage, the patient is still able to cope with daily social or other activities because the forgetfulness may only be a minor annoyance, and is generally not severe enough to alert family members, so very few patients seek medical attention at this stage. Although the early psychiatric symptoms of dementia are not obvious, one sign that deserves the attention of family members and doctors is that the patient does not recognize his or her own memory loss and intellectual deterioration, a phenomenon that psychiatry refers to as a lack of self-awareness. After a few months to one or two years, other symptoms of dementia gradually become apparent, such as excessive selfishness, growing coldness toward loved ones, eccentricity and irritability, suspicion that items have been stolen because they have forgotten where they were stored, suspicion that family members are behind their backs or harming their own interests, progressive decline in the ability to take care of one’s own life, constant wandering around the house, and a lack of self-awareness. The patient’s ability to take care of his/her personal life declines, he/she wanders around the house, gets lost when going out, and his/her sleep pattern is abnormal. As the disease progresses further, the patient’s memory loss and mental deterioration become more and more serious, and he or she forgets not only recent events but also many things in the past, and cannot even correctly recognize family members with whom he or she has lived for a long time. After several years or even one or two decades of illness, Alzheimer’s disease is often caused by neurological damage resulting in paralysis, incontinence, and so on, which in turn leads to lung infections, urinary tract infections, bedsore infections, and so on, and ultimately death from such comorbidities. For most older people, forgetfulness is a natural part of the normal aging process. This type of forgetfulness, which some call benign senile forgetfulness, is characterized by poor but relatively stable memory rather than progressive aggravation, and these older people have a clear understanding of their own memory loss and seek medical attention for it. Since amnesia, especially forgetfulness of recent events, is a very early symptom of dementia, and modern psychiatry has the therapeutic tools to mitigate memory loss in dementia and to slow down the progression of dementia, early and aggressive treatment of memory loss in dementia is necessary to slow down the progression of dementia and to improve the quality of life of dementia patients and their families. When we find that the elderly people we are familiar with have memory loss, we should be highly vigilant that this is likely to be an early sign of dementia. Modern psychiatry has many methods to measure the degree of memory loss and can determine whether such memory loss is a manifestation of dementia based on the degree and rate of development of memory loss.