Muhammad Ali's doctor claims that the boxing great's remarkable career in the ring could not have contributed to the former champion's Parkinson's Disease.
It has long been asserted that the effect of taking punishing head blows in fights against the likes of George Foreman in the 'Rumble in the Jungle', whose 40th anniversary was celebrated this week, have been a key factor in Ali suffering from Parkinson's, a neurological condition which can cause its sufferers to shake and have problems with their balance.
However, plenty of Parkinson's victims have not suffered anything like the head trauma that came Ali's way during a 21-year ring career.
And Dr Abraham Lieberman, the Medical Director of the Muhammad Ali Parkinson Centre, said Sunday it was impossible to be sure regarding the root cause of American sporting hero Ali's condition.
"It's only over the last 10 years that he's had a lot of trouble walking, with falls," Lieberman told BBC Radio Five Live's Sportsweek programme.
"So his course has been more that of typical Parkinson's Disease. If you look at the MRI of his brain it looks pretty good but it's very difficult to factor in what sort of role did boxing play.
"People ask me about this and I tell them: look at George Foreman. He boxed longer than Muhammad did, took many more blows to the head and he's on television selling his cookware.
"I think that he (Ali) has typical Parkinson's Disease. Did the boxing contribute? I don't know. It may have."
Lieberman added: "He's had Parkinson's since about 1984, that's almost 30 years, that's a long time in Parkinson's.
"He's in good spirits, he has some trouble walking but overall for having had Parkinson's for 30 years, he's doing OK.
"Muhammad is now 72 so you can have a heart attack or you can have a stroke.
"I don't know that he's more or less at risk than anyone else but anything can happen to you," said Lieberman of Ali, who at the height of his fame could lay claim to being the most famous man on earth.
"How do people with Parkinson's Disease die? They don't die of Parkinson's Disease, they develop trouble swallowing and they develop pneumonia and he doesn't have trouble swallowing.
"They fall, they bang their head -- his family takes extraordinary care of him.
"I could have a heart attack or a stroke and die but I don't see anything immediately that leads me to think he's gong to die in six months or die in a year. I can't say that."