Glen Campbell's Alzheimer's diagnosis puts spotlight on grim illness

Caption: SYDNEY, AUSTRALIA - JANUARY 30: Musician Glen Campbell performs during a photo call at the Shangri-La Hotel Sydney on January 30, 2008 in Sydney, Australia.
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glen campbell
Glen Campbell on stage in Sydney, Australia on Jan. 30, 2008
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(CBS) Glen Campbell, the country music icon, has Alzheimer's disease and is preparing a farewell tour. Why go public with the diagnosis? "If he flubs a lyric or gets confused on stage, I wouldn't want people to think, 'What's the matter with him? Is he drunk?'" Campbell's wife, Kim, told People magazine.

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Campbell, 75, whose hits include "Rhinestone Cowboy" and "Gentle on My Mind," has experienced memory problems in the past but got the bad news only six months ago.

It is a devastating diagnosis. An irreversible brain disease, Alzheimer's slowly destroys memory and cognition and eventually makes it impossible to carry out the simplest tasks of everyday life. Doctors don't know the precise causes of Alzheimer's, which affects an estimated 5 million Americans, but suspect that heredity and "lifestyle factors" play a role. These include high blood pressure, diabetes, obesity, and other chronic conditions.

Four prescription medications have been approved for the treatment of Alzheimer's. But while the drugs can help maintain mental function and curb behavioral problems for a few months to a few years, they do nothing to change the underlying disease process.

How long does Campbell have? No one knows. But the Alzheimer's Association says that people with Alzheimer's live eight years, on average, after their symptoms become noticeable to others.

But Campbell isn't laying down his guitar just yet.

"I still love making music," he said. "And I still love performing for my fans."