Dementia is an acquired disease, referring to cognitive dysfunction, i.e., decreased learning ability and decreased executive ability. The most common ways to determine this are as follows: 1. Memory changes: recent and long-term memory loss; 2. Decreased executive ability: disorganization and inability to complete complex tasks; 3. Orientation disorders: such as time and place orientation disorders, not knowing the location and time; 4. Language disorders: manifested by decreased language ability and difficulty in expression, and in severe cases, even leading to the impact on all aspects of life.