The early signs of dementia, or Alzheimer’s disease, may include memory loss, visuospatial impairment, executive impairment, and personality changes. Its prevention and treatment mainly lies in medication and through changing one’s behavior or lifestyle. 1. Early symptoms (1) Memory impairment: firstly, near-term memory loss occurs, often forgetting things done in daily life and some commonly used items. As the disease progresses, distant memory loss occurs, i.e. forgetting things and people that have happened for a long time. (2) Visuospatial impairment: some patients may have, after going out, can not find the way home, and can not accurately copy stereograms. (3) Executive impairment: easily fatigue, anxiety and negative emotion in the face of rudimentary and complicated things. (4) Personality change: becoming unclean, unkempt, irritable, irritable, selfish and suspicious. 2.Prevention and treatment (1) Alzheimer’s disease cannot be completely cured at present, but medication can improve symptoms, help improve quality of life, enhance the ability to perform daily activities, and reduce the burden on caregivers. Commonly used drugs include donepezil, memantine, olanzapine, citalopram, etc. Specific drugs should be used under the guidance of a physician. (2) Currently there is no way to prevent Alzheimer’s disease, but it is important to prevent the disease through some healthy habits. For example, lowering blood pressure, sugar and fat treatment, avoiding exposure to drugs that may induce the disease, controlling body weight, Mediterranean diet, and paying attention to rest. Alzheimer’s disease starts insidiously and progresses slowly. Patients or their family members are advised to consult a doctor in time to avoid delaying the treatment of the disease if they find that their memory is impaired or their executive ability decreases.