Dementia currently has two main common subtypes, as follows: 1, Alzheimer’s disease: Alzheimer’s disease is a group of primary, degenerative, progressive degenerative brain diseases, the main manifestation of brain intelligence decompensation, the patient will appear degenerative changes in brain neurons, ventricular enlargement, atrophy of the cerebral cortex. If the dementia occurs before the age of 65, it is called early-onset dementia, and if it occurs after the age of 65, it is called late-onset dementia; 2. Vascular dementia: multiple cerebral infarcts can cause vascular dementia because the infarction of blood vessels causes local brain tissue neuronal ischemia and hypoxia, neuronal destruction, local brain intelligence and brain function are seriously affected, and diminished intelligence occurs. These are the two more common types of dementia in clinical practice.