Cats with Alzheimers?

I know that a large percentage of older dogs get CDS (Canine Dysfunctional Disease) which is similar to Alzheimers in humans. Our 17 year old Shih Tzu had it for about a year before he died. He would wander around like he didn't know where he was, stare at the walls and get lost in a corner of a room or behind a door and have no idea how to get out of there. Now one of my 19 year old cats is showing the same symptoms. I had not heard about this in cats, but it stands to reason that, if they live that long, they will start to deteriorate mentally as well as physically. Thank heavens he still remembers where to find the litter box. His litter brother so far has not shown any symptoms. I don't believe in letting my cats outdoors so they have never been exposed to all the diseases and dangers out there, so maybe that explains their longevity. Aside from being arthritic they are both in good health considering their age. Interestingly enough I have never noticed a hearing loss in older cats like I have with older dogs (and people).