Sir Ian McKellen is worried memory loss will force him to quit acting.
The 76-year-old actor believes he'll eventually struggle to remember his lines and is terrified he will have no choice but to park his career because of it.
He explained: "I don't have that problem, yet. I say yet because it does seem to be inevitable. I expect that one day, because it's happened to my friends, that learning will be such a worry that I'll have to stop acting."
However, the 'X-Men' star has already started taking precautions against the natural effects of ageing by installing a small stair lift in his London home.
He added to the Times newspaper's magazine: "I don't use it but I shall use it when I need to use it."
Meanwhile, Sir Ian, who came out as gay 29 years ago after hiding it from world for most of his life, has admitted he finds fame quite "comforting."
He said: "As someone who started out life pretty shy, and who is still pretty shy, it's very comforting to be known.
"You'll walk into a room, some people come up and say hello and tell you why they're saying hello, because they liked a play or a film and I know where I am."