WASHINGTON •Former United States president Bill Clinton once praised singer Glen Campbell for his courage in becoming a public face of Alzheimer's disease.
The devastating impact of the ailment was revealed, among other details, in the 2014 documentary, Glen Campbell: I'll Be Me.
On Tuesday, the country music legend and mellow-voiced Rhinestone Cowboy, who sold millions of albums over a career that spanned decades, died at age 81 after a long battle with the disease.
His death was met with an outpouring of grief from stars of the country music world and others.
"Glen Campbell was one of the greatest voices of all time. I will always love you," Dolly Parton wrote on Twitter.
"Thank you @GlenCampbell for the artistry, grace & class you brought to country music. You were a shining light in so many ways," country star Brad Paisley tweeted.
Campbell left his mark on the music, television and movie worlds.
His more than 70 albums sold more than 50 million copies, earning six Grammy Awards, including a Lifetime Achievement Award, and membership in the Country Music Hall Of Fame and Musicians Hall Of Fame.
Completed while he was already suffering from the ravages of Alzheimer's, his final album, Adios, was released in June. He cut the album in 2012 after completing a difficult final tour, which was documented in the 2014 documentary.
The film, which generated the Grammy-winning song, I'm Not Gonna Miss You, showed the star still instinctively fluent on the guitar yet struggling to remember lyrics and set lists. By the time of his final show in Napa, California, he was barely able to lead his band.
Glen Travis Campbell was born on April 22, 1936, in a small town in Arkansas, the seventh of 12 children of a struggling sharecropper.
According to his website, his father recognised his talent at an early age and bought him a US$5 guitar when he was four. He was taught to play by his Uncle Boo.
Campbell left home at 14, performing on radio and TV in Albuquerque, New Mexico, before landing in Los Angeles in 1960.
There, he performed as a session musician with Phil Spector's legendary backing band, The Wrecking Crew, helping to produce what was called the Wall of Sound.
Campbell performed on tracks for stars such as Elvis Presley and Frank Sinatra. His smooth guitar licks can be heard on the Righteous Brothers hit, You've Lost That Lovin' Feeling and The Beach Boys' Pet Sounds album.
He toured with The Beach Boys in 1964 after singer Brian Wilson temporarily retired from the band.
His breakout success came in 1967 with the song, Gentle On My Mind. His album, By The Time I Get To Phoenix, was named Album of the Year at the 1968 Grammy Awards.
He hosted his own television show - The Glen Campbell Goodtime Hour - from 1969 to 1972 and took his chiselled good looks to Hollywood.
He appeared in the classic 1969 western, True Grit, playing the role of La Boeuf, a Texas Ranger who partners John Wayne's Rooster Cogburn in search of a killer.
Campbell's best-selling single, Rhinestone Cowboy, was released in 1975 and has sold more than five million copies.
Married four times, he had eight children and well-publicised struggles with drinking and drugs.
He chronicled his fight with alcohol and cocaine addiction in his 1994 autobiography, Rhinestone Cowboy.
He credited his marriage to his fourth wife, Kim, and his embrace of Christianity with helping him reach sobriety.
As news spread of his death, Arizona Senator John McCain also paid tribute to the singer. "Glen Campbell, a great entertainer, a great man & a great Arizonan - thanks for the memories," he tweeted.