The age at when most dogs get dementia is around 10 to 12 years of age depending on the dogs lifespan.
If the dogs lifespan is around 13 to 15 years then the dog may get dementia when they are 10 to 12 years old and continue to have the dog dementia until they die.
If the dogs lifespan is around 20 years then they may get the dog dementia at around age 15 years old if they are gonna get it.
Not all dogs get dementia as they age just like not all humans get dementia in old age but dog dementia is pretty common.
If you notice your dog is getting confused or you notice signs of the dog developing dementia such as circling, wandering and house soiling then your dog likely has dementia especially if they are nearing the end of their life.
A few other symptoms of dog dementia include include lethargy, sleep disorders, decreased learning and vocalizing.