thanks a bunch guys! Dementia is early onset, but really what we think happened today was what has happened to him a couple times now over the last couple years. An ischemic mini stroke. The firs time he had that, he couldn't talk for about a day, the symptoms cleared up on their own.  He then had another minor episode of it. Each time it happens his blood pressure is really high. 

So the first thing I did was take his blood pressure, it was 195 / 95, pretty high. gave him some aspirin and it started to come down, was 145 / 85 when I left. Decided not to take him to the hospital since it was coming down and will call his doctor in the morning. 

when these things happen his mind is gone for a while. Today he insisted that he went to my brothers office to empty the trash - which he did not. When I was at this place and gave him the aspirin, 20 min later he suggested that he take some aspirin and when I told him Dad I already had you take some 20 min ago, he insisted that I did not. Usually once this ischemic clears up his mind clears up too.

Of course one day we worry that it won't or will go into full blown stroke etc