How Alzheimer's start

Alzheimer's starts with a sticky protein called 'amyloid beta.' It will bind to itself and form 'amyloid plaques.' If you have enough amyloid plaques accumulated in your brain, it will reach a tipping point at some stage that causes neurofibrillary tangles, neuroinflammation, cell death, and other symptoms we classically know as Alzheimer's.

Before that tipping point, you're symptom-free. After the tipping point, the glitches in memory formation and retrieval are different.