I don't know much about the medical concept of the disease, but I know that it is something to do with a buildup of something in your brain, which causes gaps in the memory portions of the brain. Alzheimers can be fought by increasing awareness.

For someone who is losing their memory, they would have no recolection of how they got to the present moment, therefore from their first person perspective, the past several years could have never happened, and they were functioning up until now in a sort of "autopilot" mode. Get him to become more aware. If he has alzheimers, I'm sad to say there's not much to do about it. But Alzheimers is a physical brain disease. Loss of memory is just as simple as increasing consciousness throuout the day, sort of how you would practice RC's. That would actually be an excellent practice for him.

Hope this helps you
--Rain