Alzheimer's disease and dementia are not the same thing: a fifth to a third of people whose brains carry the pathology never became demented.

Alzheimer's disease does not necessarily equal dementia. people can have Alzheimer's disease and not get dementia. So, we found this out from post-mortem studies. People have been followed as they age. Uh they've donated their brains and it turns out that perhaps 20 to 30% of these individuals who never had dementia have Alzheimer pathology.