Can alzheimer's happen to young people?

Not common: Except for those with down's syndrome, alzheimer's usually occurs after age 50 and most often after age 65. It is most common in those older than 85.

Rarely: There are some families with bad genes where several members develop alzheimer's disease at an early age but they are quite rate.

Less commonly: Typically, Alzheimer's disease is a progressive neurological problem with symptom onset usually occurring in one's 70s or 80s. However, in about ~4% of all Alzheimer's cases, symptoms start age less than 65, termed "early-onset" Alzheimer's disease. About 5% of all Alzheimer's cases are due to a genetic mutation, and, many of these patients show symptoms in earlier age, sometimes in their 40s and 50s.