American singing star Glen Campbell is suffering from Alzheimer's disease.
The 75-year-old and his wife Kim revealed the singer's condition in People magazine in the US.
Kim Campbell said: "Glen is still an awesome guitar player and singer. 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 Grammy winner, whose Rhinestone Cowboy topped the charts in 1975, had been suffering from short-term memory loss for years, but the Alzheimer's diagnosis came only six months ago.
Campbell said: "I still love making music, and I still love performing for my fans. I'd like to thank them for sticking with me through thick and thin."
A spokesman for Campbell in the UK said that he would say goodbye to his British fans this autumn.
Campbell said: "I'm coming back to perform in the UK, where I have had the pleasure of touring regularly over the past 40 years, for my final tour there.
"I'm thrilled to be returning. The audiences were wonderful on my previous tours, and I always felt right at home. They always make me feel appreciated."
Glen Campbell: The Goodbye Tour will see him supported by his two daughters and his son's band, performing many of his greatest hits, which include Gentle On My Mind, By The Time I Get To Phoenix, Wichita Lineman, Galveston, Rhinestone Cowboy and Southern Nights.
The tour opens on Friday October 21 at the Lowry in Salford and plays 15 cities, including London's Royal Festival Hall on Saturday October 22.