Acting disoriented or lost
Vocalizing, often at night
Staring off into space while looking at a wall or corner
Forgetting to eat or drink unless food bowls are put in front of them
Going to the bathroom outside the litterbox
Changes in sleep cycle, being awake and active in the middle of the night
Unusual interactions with other pets or family members (becoming more needy, more reactive, or more aloof)
Forgetting that they have just been fed and asking to eat again
Poor grooming habits
Sleeping more than usual
Symptoms of dementia in cats include:
Except for poor grooming habits and going to the bathroom outside the litterbox most of those are pretty much normal cat behaviour…
For real, if that list should be believed, then all my past cats had early onset dementia.