Yeah, even with those limitations, it's still possible that the relationship between plaque buildup and Alzheimer could be similar to the one between smoking an

Yeah, even with those limitations, it's still possible that the relationship between plaque buildup and Alzheimer could be similar to the one between smoking and lung cancer - you can get the latter without the former (randomly or triggered by other causes), you can have the former without getting the latter, but in most people, the former will massively increase the risk of getting the latter. Then again, the plaque could also be a co-symptom caused by some third factor. We'll see eventually