I tend to steer clear of vegetarian proponents, as I find their hectoring approach a tad annoying, however, having a number of vegetarians of varying degrees in my immediate family, I'm not unacquainted!
I also find those who promote various theories about the causes of dementia to be similarly irking [certain newspapers, etc], for much the same reason - statements of supposition presented as absolute fact.
However, the fact is [or is it supposition?
] there must be a cause for dementia, and until sufficient avenues have been explored and tested and proved, then all things are possible, from tin foil to chocolate digestives.
To reply to the topic of this thread, I don't know of any vegetarians who have dementia, but since I tend not to be in their company, how would I know? When I mentioned this thread to my vegetarian step-daughter, she just looked at me meaningfully. Later she emailed me with the following link
http://www.goveg.com/alzheimers_madcow.asp
I place no validity - or non-validity - on the content of the site above. Simply another theory. As a person who likes small amounts of best quality meat, and substantial vegetable content with it, I'm interested, but generally distrustful of unproven theories.