Bellgirl - Alzheimer's Disease is what used to be called "pre-senile dementia". The reason I mentioned it in relation to the posts on NBC possibly having dementia is that he is only 69 - young to get the classical "senile dementia". And the point I was actually making was that I know of people who DO have mild Alzheimers who continue to drive quite OK.
It is a type of dementia that tends to come on earlier in life, and tends to affect those over 65. The incidence rises once over about 85. It is one of a group of conditions collectively termed "dementias". Some are metabolic, some are physical damage in the brain (Alzheimer's is thought to be one of those), and some are quite a mystery - just the functional deterioration.
Many people as they get older - and I'm talking over 75-80 broadly - will show signs on a CT scan (or MRI) of the brain such as atrophy of the brain, particularly the gyri and sulci on the surface of the cerebral hemispheres.
But basically, the dementias comprise a group of conditions, the common features being deteriorating brain function, particularly memory. Alzheimer's is one of these.
Hope that makes sense.
And no - I don't think NBC has dementia, Alzheimer's or otherwise, although I'm not a neurologist and I haven't examined him.
EDIT: Here's a brief summary of just a few of the different types of dementia:
http://www.fightdementia.org.au/understanding-dementia/types-of-dementia.aspx
'NOTHER EDIT: I see Bellgirl's original post was deleted, and I didn't quote it in mine, so in case my post doesn't make much sense, she was just asking about Alzheimer's and how it related to the more general term of "dementia"..... Maybe this information is useful for those who have been discussing dementia, although I don't think it pertains to this case. If the Mods think it better just to delete this post, then please feel free to do so.