I came across an article that explained how Japanese scientists found genes in older cats that are present in human Alzheimer's patients!
They also found the chemical peptide AB42, which causes mental deterioration, in the cats. The animals they examined were wild (taken from the streets) and deceased, so they couldn't monitor how they acted when alive, but they want to conduct studies on house cats, "which have been known to become irritable, forget their food, walk sideways and display other aging behaviors."
The article also said that other animals, like dogs, have been suspected to have dementia-like symptoms as they age.

The way to prevent this is the same as for humans; a well-balanced diet, stimulation, and lots of love! It's funny how similar animals and humans can be...
I've read that article and I believe they definitely can form dementia. I've had friends online with senior kitties or sick kitties that developed it.
Thanks for this bit of info. It's amazing, isn't it. Regardless if the species you belong to, you should never play jokes with mother nature eat what isn't meant for your species, otherwise trouble is brewing.