What Would Make An Old Dog Pace All Night Long Then Sleep All Day?

I hope this is not too late.  Your dog has cognitive dysfunction.  My 14 2/2 yr old dog had it, too.  Unfortunately, his came on suddenly and we realized what it was too late.  There is a medication to fix the problem in 75% of dogs.  It takes a month to work.  My dog had horrible anxiety with his sleeplessness and I had to put him down as a result- I could not make him go through a month of anxiety for a medicine which might not have worked.  I hope this helps someone.  Other symptoms include:  Anxiety, getting "stuck" in corners, going to the hinge side of the door to go out, forgetting house training, and no responsiveness to affection.

Major causes of pacing in dogs is pain and bloat. This pain can be due to

1. Muscular and skeletal problems
2. Disc injury
3. Traumatic injury
4. Damage and inflammation of the tissues
5. Exposure to heat and cold
6. Some diseases

Both pain and bloating requires vet visit for diagnose and treatment

Hes getting old and his bod doesn't work like it used to

Anxiety or maybe he has his days and nights mixed up