The most common type of dementia is Alzheimer’s disease (Alzheimer’s). The typical onset symptom is memory impairment. Patients forget events that have just occurred (poor short-term memory), while older memories (long-term memory) are relatively unaffected at the onset. Since most people with dementia may experience confusion, it is possible that the patient may have confusion symptoms. Although confusion may be alleviated by close care, improved living conditions and diet, psychiatric medications can also help stabilize mood, reduce hallucinations and delusions, or impulse control. However, medications have not yet been able to slow brain degeneration. People with dementia are also often depressed and should be diagnosed and treated by a medical professional. Age is the most important risk factor for dementia. According to epidemiological studies, 5% of people over the age of 65 have dementia, increasing to 20% over the age of 85. It is a syndrome caused by a slowly progressive brain disease. It is characterized by disturbances in multiple higher cortical functions, including memory, thinking, orientation, comprehension, calculation, judgment, speech and learning. Clear consciousness, poor emotional self-control, and social or motivational decline often accompany, but sometimes precede, the onset of cognitive impairment. Dementia is a secondary decline in intelligence caused by brain damage after considerable development of intelligence, and can be caused by a variety of organic factors. Dementia is not diagnosed before the age of 18 years. Clinical manifestations Near-memory deficits are often the earliest clinical manifestations, mainly impaired memory function, where the patient is unable to remember scheduled appointments or tasks, or recent events. However, patients are self-aware of this and seek to conceal and compensate for it, often taking a series of auxiliary measures, such as taking painstakingly detailed written notes or uncharacteristically asking for reminders, thus reducing or avoiding the adverse effects of the memory deficit on work, society and life, and thus masking the memory loss as a symptomatic manifestation. Another early symptom of dementia is the reduced ability to learn new knowledge and acquire new skills, and the tendency to feel tired, frustrated and irritated when encountering unfamiliar assignments. The ability to think abstractly, generalize, synthesize, analyze and judge is progressively diminished. The overall involvement of memory and deficits in comprehension and judgment may cause delusions that are brief, variable and unsystematic, usually about theft, loss, suspicion of illness, victimization or jealousy of a spouse. Impairment of memory and judgment may result in a fixation disorder in which the patient loses the ability to recognize time, place, people, or even himself. Therefore, they are often indistinguishable from day to night, do not know the way back or wander aimlessly. Emotionally, the patient shows emotional instability in the early stage and gradually becomes indifferent and slow in the evolution of the disease. Sometimes the emotions lose control and become superficial and changeable. They may be anxious, depressed, passive, indifferent, or angry, prone to crying and laughing, and unable to control themselves. Higher emotional activities, such as shame, moral responsibility and honor, are the most affected. Personality disorders sometimes appear early in the course of the disease. Patients become less energetic, easily fatigued, lose enthusiasm for work, lose interest in activities they used to enjoy, seem inattentive to people and things, sometimes make bad jokes that are out of place, do not pay as much attention to dress and grooming as before, and may become untidy and unkempt. Sometimes there are violations of social and moral norms such as molestation of young children or exposure of the pubic area. Some people become suspicious, stubborn and calculating. Some patients do not recognize their spouse or children, and they lose their orientation to time and place, and often wander off. In the end, patients die from infections, internal diseases or failure.