Country music superstar Glen Campbell revealed that he was battling Alzheimer's in June of 2011, when he announced a farewell tour. The veteran entertainer played the final dates of that tour last year, and according to his family, they will stand as the final dates of his performing career. In a new interview, Campbell's wife and daughter share that the world-renowned singer and instrumentalist's disease has progressed to the point where he can no longer perform.

Campbell's wife Kim tells Country Weekly that he now has trouble speaking and requires constant attention, adding that his advancing disease has brought on side effects including anxiety, agitation and depression.

"One time, he couldn't use the television remote," she reveals. "He knew what it was but couldn't figure out how to use it. And he got so agitated that he threw the remote at the television."

After getting his start as one of the top on-call studio session aces in the music business in the '60s, Campbell shot to solo superstardom later in the decade and in the '70s with a string of hits including 'Galveston,' 'Wichita Lineman,' 'Gentle on My Mind' and 'Rhinestone Cowboy.' He hosted a top-rated weekly variety show, starred in 'True Grit' with John Wayne and performed sold-out concerts all over the world. His success across multiple genres made him perhaps the first true crossover country star. In more recent years he has continued to perform well-received concerts, as well as occasionally releasing new music.

His daughter Ashley says his advancing Alzheimer's has compromised his musical abilities, noting that when she toured with him in 2011, he would often forget the words to his own songs while onstage. "It's heartbreaking to see this disease robbing him of what he does best," she states.

The singer recently released 'Ghost on the Canvas,' his critically acclaimed final studio album. As for Campbell's long-term prognosis, wife Kim says she doesn't know what the future may hold, saying only, "I just go day to day and try to keep him happy and healthy."

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