Examining loss of use and recognition in patients with Alzheimer’s disease is difficult, and it is difficult to distinguish them from incompetence due to aphasia, visuospatial skill impairment, and amnesia. About 1/3 of patients have visual aphasia. Those with facial cognitive inability do not recognize the faces of loved ones and familiar friends. Impaired self-awareness can lead to the mirror sign, in which the patient sits in front of a mirror and talks to his or her own image, even asking the image “who are you? The causes of Alzheimer’s disease are not well understood, but there are many known causes of dementia in the elderly. Brain degenerative diseases: There are many kinds of dementia caused by brain degenerative diseases, the most common one is Alzheimer’s disease dementia, which is also called early senile dementia when it develops in the early age. The onset of dementia is slow and progressive. In addition, there are Pick’s disease, Tinton’s chorea dementia, progressive supranuclear palsy, Parkinson’s disease dementia, and so on. These latter dementias are relatively rare. 2. Cerebrovascular disease: The most common ones are multiple cerebral infarct dementia, which is caused by a series of multiple minor cerebral ischemic attacks that accumulate many times and cause substantial cerebral infarction. In addition, there are subcortical vascular dementia and acute onset cerebrovascular dementia, which can rapidly develop into dementia after a series of strokes caused by cerebral hemorrhage and cerebral embolism, and a few can also be caused by a single large cerebral infarction. In short, cerebrovascular disease is also a more common cause of dementia. 3, genetic factors: Many studies at home and abroad have proved that the offspring of Alzheimer’s patients have more chances to suffer from this disease. However, the mode of inheritance is still unclear. Some people believe that it is dominant genetic inheritance; others believe that it is recessive genetic inheritance; others believe that it is polygenic autosomal recessive inheritance, and the genetic effect can be restricted by environmental factors and mutations of genetic factors, so as to interrupt its genetic effect. There are also some studies that dementia is a non-genetic disease, such as vascular dementia is not directly related to heredity. 4, endocrine disorders: such as hypothyroidism and parathyroidism may cause dementia. 5.Nutritional and metabolic disorders: The brain tissue and its functions are damaged due to nutritional and metabolic disorders, which lead to dementia. Such as various organ-induced encephalopathy, like nephrogenic encephalopathy, which is chronic renal failure and uremia causing ischemia and hypoxia in the brain, can lead to dementia; others such as hepatic encephalopathy and pulmonary encephalopathy can lead to dementia. Severe nutritional deficiencies, such as vitamin B1 and B12, as well as niacin and folic acid deficiencies, can lead to dementia. Diabetes and hyperlipidemia can cause atherosclerosis in large and medium arteries, and thickening of the basement membrane of small vessels and microvessels can cause cerebral infarction and cerebral hemorrhage, leading to vascular dementia. 6, tumors: malignant tumors can cause metabolic disorders that can lead to dementia, and brain tumors can also directly damage brain tissue and lead to dementia. 7, drugs and other substances poisoning: alcoholism, chronic sprinkler poisoning caused by Alzheimer’s disease is not uncommon, in is not yet recognized. Long-term exposure to aluminum, mercury, gold, silver, arsenic and lead, etc., poorly protected, causing chronic poisoning can lead to dementia. Carbon monoxide poisoning is also a common cause of acute dementia. 8, AIDS: AIDS is one of the causes of dementia. It is known that the elderly can develop progressive dementia in the early stages of AIDS, and it has been proved that the central nervous system can be directly infected with human immunodeficiency virus (HIV). 9, syphilis: syphilis spirochetes can invade the brain, producing mental and neurological symptoms and eventually leading to paralysis and increasing mental retardation and personality changes, the so-called paralytic dementia. 10, other: traumatic brain injury, persistent seizures of epilepsy, and normal pressure hydrocephalus and other causes can cause dementia. In addition, long-term emotional depression, isolation, widowhood, illiteracy, low language level, lack of physical and mental exercise in the elderly can also accelerate the process of brain aging and induce dementia.