Isn't it possible that the processes resulting in AD begins many years before symptoms appear, and that deposits of amyloid plaque are an early sign of these processes, i.e., that plaque does not immediately cause cognitive decline and dementia, thus, it can be present in the brains of individuals who do not present any symptoms of AD (but who would eventually do so if they lived long enough)?

My mother died of AD last week. She only began showing symptoms in October of last year.

Ever?