The 63-year-old, dubbed The Greatest, was diagnosed with the disease 20 years ago, and is slowly slipping away from his family.
Boxer Laila, 27, explains, "It is painful for me because I would love to sit down and talk to my dad about the way he used to be when he was my age, when he was in his prime, because we are so much alike.
"I can't really do that. I can't share a lot of things with him.
"I feel like the disease is progressing. Different things start happening as you get older. I have noticed a change in him, something that goes along with Parkinson's.
"He has his good days and his bad days. He's taking a lot of different medications. Sometimes, his speech is so slurred, you can't hardly understand him. But he definitely knows what's going on. That's for sure. He sees everything."
Ali is currently undergoing therapy for neck and back problems at his home in Berrien Springs, Michigan.
His manager Howard Bingham adds, "Laila feels she is slowly losing him."
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