The 75-year old singer and his wife, Kim, told the magazine that they wanted to come forward now because Campbell is hoping to perform in a number of farewell shows this fall.
Glen is still an awesome guitar player and singer, Kim told People. But 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?'
The couple said that Campbell received the official Alzheimer's diagnosis six months ago, but had been suffering from short-term memory loss for some time before that.
Alzheimer's is the leading cause of dementia, and is a degenerative disease, although it does not proceed at the same pace for every person. A singular cause of Alzheimer's is still not known, although intensive research efforts have been devoted to identifying the cause and possible cures for the disease.
Campbell is best known for a series of hits in the 1960s and 1970s: His best selling single, Rhinestone Cowboy, sold 2 million copies within months of its 1975 release.