Why does Alzheimer's disease typically affect older adults?

I understand the basics of Alzheimer's disease, but I am curious as to why it is typically found in older or elderly adults. I know that as we age our cells change and they can mutate or deteriorate. Since this can happen at any age, I am wondering why dementia disorders are less common in children and young adults. I mean, theorectically, a child could develop Alzheimer's disease, could they not?

[margypops]

Maybe it does and it is called something else, you may get a better answer on  the expert/Doctor forum good Luck

[Yvette BG]

There are risk factors for getting Alzheimer's which tend to occur as we get older or hit us at middle age and then get worse if not properly treated---like high blood cholesterol, high blood sugar/diabetes, and high blood pressure.