The actor's character slowly becomes senile in the film and relies on the young son of the owners of the old-folks’ home he resides in to help him stay lucid.
And Caine admits he didn't have to dig too deep for the role - because he watched his friend struggle with memory loss.
He tells the Los Angeles Times newspaper, "One of my closest friends - he was only 68 - just died of Alzheimer’s... Dougie having dementia was a reason I wanted to do it (film).
"But, also, from a purely selfish point of view, it was a hell of a part to do. I’m now looking for things that are different and stretch me. I don’t work very much. So a movie sort of has to grab me."
Caine is thrilled with the film, but the same can't be said for his wife Shakira: "She got very upset, because she watched me grow old and die. I said, 'It’s a performance. I am not like him. I am not the same person.'"