Dementia is a syndrome of acquired progressive cognitive dysfunction that affects the content of consciousness rather than the level of consciousness, with varying degrees of intellectual impairment including memory, language, and visuospatial functions, personality abnormalities and decreased cognitive (generalization, calculation, judgment, synthesis, and problem solving) abilities, often accompanied by behavioral and emotional abnormalities, and a significant decrease in the patient’s ability to perform daily living, social, and work activities. The incidence and prevalence of dementia increases with age. Studies on the prevalence of dementia in the elderly population have been conducted in many countries, and the results show that the prevalence of dementia is 1% in people over 60 years of age, between 2% and 7% in people over 65 years of age, and more than 40% in people over 85 years of age. The prevalence of Alzheimer’s disease (AD) is higher among women, and the prevalence increases with age above 65 years, and increases almost 1 times with each additional 5 years. The prevalence of dementia in China is 0.75%-4.69% in people over 60 years old, and with the aging of our population, the incidence of dementia in old age is on the rise, and the cost of its treatment and care is high, bringing a heavy burden to society and families. Early prevention and diagnosis and treatment of early cognitive impairment have positive social significance. For this reason, the Beijing Municipal Health Bureau has organized a guide for the prevention and treatment of Alzheimer’s disease in the Beijing community, with the aim of increasing awareness of the disease among community health institutions and families, popularizing the management of Alzheimer’s patients, and guiding community physicians to better solve practical problems. The causes of Alzheimer’s disease include degenerative and non-degenerative diseases, the former including Alzheimer’s disease frontotemporal dementia, Lewy body dementia, Parkinson’s disease combined with dementia, Pick’s disease, etc. The latter includes vascular dementia, infectious dementia, dementia due to metabolic or toxic encephalopathy, etc. Alzheimer’s disease is the most common cause, and it is now generally considered that vascular dementia takes the second place, and other types of dementia are less Other types of dementia are less common. The prevalence and disability of Alzheimer’s disease are high, the course of the disease is long, and the cost of treatment is large, which places a huge burden on the patient’s family and society. The Beijing Municipal Health Bureau has organized this book to raise awareness of this syndrome in the community, especially among grassroots community health workers, and to provide reasonable support and care for patients with dementia, and to actively promote community-based elderly care in Beijing.