What is early-onset dementia?

Early onset dementia, also called younger-onset dementia, is dementia that begins before age 65. The Alzheimer's Association says younger-onset Alzheimer's affects people under 65 and that many are in their 40s and 50s, often with families and careers. Because doctors do not usually look for dementia in younger people, getting an accurate diagnosis can be slow, and symptoms may be blamed on stress.

Early onset dementia means symptoms begin before age 65. MedlinePlus says the signs of early-onset Alzheimer's disease appear between a person's thirties and mid-sixties, and that this form accounts for less than 10 percent of all Alzheimer's cases. The Alzheimer's Association notes that many people with younger-onset Alzheimer's are in their 40s and 50s, and they can be in any stage of the disease.

Sometimes, but usually not. MedlinePlus explains that some early-onset Alzheimer's is caused by variants in the APP, PSEN1 or PSEN2 genes, inherited in an autosomal dominant pattern, so one altered copy from one parent is enough. The Alzheimer's Association says these genes have been found in a few hundred families worldwide, and that doctors do not understand why most early-onset cases occur.

No. The Alzheimer's Association says Alzheimer's, the most common cause of dementia, has no cure. Two treatments, donanemab and lecanemab, remove beta-amyloid from the brain and slow decline in people with early Alzheimer's, and other treatments can temporarily ease symptoms and improve quality of life. Some memory problems have treatable causes, which is why a thorough medical evaluation matters at any age.

It varies widely. The Alzheimer's Association says a person with Alzheimer's lives four to eight years after diagnosis on average but can live as long as 20 years. MedlinePlus says survival is usually 8 to 10 years after symptoms appear, ranging from 1 to 25 years, and is usually shorter in people diagnosed after 80 than in those diagnosed younger. A doctor can speak to one person's outlook.