Alan Alda has Parkinson's disease.

The 82-year-old actor - who is best known for his role as Army Capt. 'Hawkeye' Pierce 'M*A*S*H' - revealed that he was diagnosed three-and-a-half years ago and said he wanted to be open about his diagnosis before someone did a ''sad'' story on him.

Speaking on CBS 'This Morning', he said: ''I was diagnosed three-and-a-half years ago and I've had a full life since then. I've acted, I've given talks, I help at the Alda Center for Communicating Science at Stony Brook. I started this new podcast. And I noticed that - I had been on television a lot in the last couple of weeks talking about the new podcast - and I could see my thumb twitch in some shots and I thought, it's probably only a matter of time before somebody does a story about this from a sad point of view, but that's not where I am.''

Parkinson's disease is a progressive neurological condition that destroys cells in the part of the brain that controls movement.

There is currently no cure and no way to slow the progression of the disease, however there are treatments including medication and surgery.

Parkinson's disease itself is not fatal, but the complications from it are dangerous.

Alan - who also starred as Presidential hopeful Arnold Vinick in 'The West Wing - has been married to his wife Arlene for 61 years and the couple have three daughters, Eve, Elizabeth and Beatrice, together.

Actor Michael J. Fox went public with his own diagnosis with the disease in 1998 and revealed he was reduced to tears when boxing legend and fellow Parkinson's sufferer Muhammad Ali - who died in 2016 - called him to offer reassurance about their shared battle.

He said: ''In this raspy, paper-thin voice, he said, 'Aahhhhh ... Michael, now that you're in it, we'll win this fight.'

''What could I say? Sitting there alone listening to Muhammad Ali, this giant - I was welling up, almost openly weeping.''