Euthanasia for pet? Mind vs body

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Our dog is diagnosed for several years with canine cognitive dysfunction (alzheimers in dogs). We have done medication, behavioral treatments, and I stopped working from the office so I can be with him. He paces for however long he can until you place him on a bed. He physically doesn’t remember how to sit, stop or lay down until he is placed on one specific bed. He is 16 years old, the only joy he has is when he eats. He refuses to play with other dogs or go for wals. However, physically his body is just fine. He is now nocturnal which means he paces all night screaming unless someone is out with him. I’m exHuated , my husband is exhausted and I just can’t do this anymore. But I feel like I owe him this since he’s been such a good boy for so long.

So the question is, do you euthanize based on mental state or wait for the body to catch up!