Actor Alan Alda revealed today that he has Parkinson’s disease, the first time he’s publicly disclosed the diagnosis he received three and a half years ago.

The MASH actor Alda made the announcement during an interview on CBS This Morning, explaining that his recent spate of TV appearances promoting his new podcast led to his decision to go public. (Watch clips from the interview below).

“I had been on television a lot in the last couple of weeks talking about the new podcast,” Alda said today, “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.”

Though he was careful not to diminish the serious, even incapacitating symptoms that Parkinson’s can bring, Alda said he wanted to warn people not to be “immobilized” by fear from the “very beginning.” He said he stays active, taking boxing lessons and even marching to Souza music.

Alda said he’s lived “a full life” since his diagnosis. “”I’ve acted, I’ve given talks, I help at the Alda Center for Communicating Science at Stony Brook.”

The 13-year-host of PBS’ Scientific American Frontiers said he requested to be tested for the disease even before his doctor noticed symptoms. He’d read that one of the early symptoms of Parkinson’s was acting out your dreams. “I was having a dream that someone was attacking me and I threw a sack of potatoes at them, but really I threw a pillow at my wife.”

Alda, whose long roster of credits also includes Crimes and Misdemeanors and The Aviator, said he approaches his condition as if it were a puzzle, figuring out each day “what do I have to adapt to, to carry on a normal life.”

Watch the interview in the three tweets below. In the first tweet, Alda announces his diagnoses at about the 1:26 mark.