Ataboy
think positive
I readied the copy of New Scientist but do not have it with me, dementia? what dementia.
Anyway it was the Nov 14th issue page 17 entitled "Mental Gymnastics" but it was a paper presented at the Society of Nuero(something) so a bit new, maybe contentious but it is something your friend can do and there are no contra-indications with drugs.
tell him to keep shouting at it, and thinking movement.
My dear old friend may reported minor strokes as her memory faded. I told the hospital that the memory loss and TIA's (as I thought) and a recent tendency to fall over were clear indications of a common cause and not a lung infection (as they said). BUT a man all in red (fresh from a Festival) is never going to have credence even if he spouts technical terms.
within days and her daughters pestering they did a scan and surprise, surprise, found a brain tumour. Now pardon me but if the tumour wasn't causing a big leasion and hogging all the blood supply, well....
mercifully she passed-on within a couple of weeks.