This is just experience talking, so by all means ask your Dad's Doctor. But, my father had been drinking heavily for 2 years. Binge drinking mostly. Well, his Dr. told me that my fathers early symptoms of Alzheimers is caused from brain shrinkage due to too much alcohol. You might check into that. Same results in the end, but you could have some leverage there if you need to use it.
Good luck and I'll be praying for you!
Lolly