Twelve years ago today, on June 22, 2011, Glen Campbell fans received sad news: They learned that the iconic singer had been diagnosed with Alzheimer's disease.

Campbell had been quietly battling Alzheimer's for a few years before he revealed his diagnosis. After the disease progressed to the point where fans might notice that Campbell was struggling, the artist and his family decided to go public with the devastating news.

“Glen is still an awesome guitar player and singer,” his wife, Kim Campbell, told People magazine at the time. “But if he flubs a lyric or gets confused onstage, I wouldn’t want people to think, ‘What’s the matter with him? Is he drunk?'"

Campbell continued with his plans to embark on a farewell tour even after his Alzheimer's diagnosis. He performed his final show on Nov. 30, 2012.

“He functions the best on stage,” Kim Campbell explained in 2012. “I think it’s where he feels the most comfortable, because everything is the same for him on the stage. He knows where he is, where the band is, where the audience is and what he’s supposed to do.”

While he was still able to communicate, the "Rhinestone Cowboy" singer became an advocate for funding the prevention and cure of the disease. To that end, Campbell traveled to Capitol Hill in 2012, along with his wife and children Ashley, Cal and Shannon.

Sadly, by early 2014, Campbell's Alzheimer's had progressed to the point where it was no longer safe for him to remain in his home, and he was moved to a facility to receive full-time care.

“You have to watch him every single second. He’s up all hours of the night and wanders,” Kim Campbell shared at the time. “He’ll pick up knives, and sometimes he won’t want to relinquish it.”

“[It can be dangerous] with all the household appliances and dish soap liquid and olive oil,” added daughter Ashley Campbell. “He’ll drink anything … if you lose concentration for a second, he could hurt himself.”

In the fall of 2015, Campbell returned home briefly, although the transition wasn't without its struggles: “He punched me in the eye, gave me a black eye — had a black eye for two weeks,” his wife told Broadway’s Electric Barnyard. “He can be combative … so that’s an ongoing challenge."

Campbell relocated to a new care facility a few months later.

“I always wanted to bring him home and give it another try because I miss him so terribly,” Kim Campbell said, but “it was just more than I could handle. He’s the sweetest person in the world, but he becomes combative when you try to change his clothes or bathe him. It really wasn’t the best situation.”

In 2014, a documentary, Glen Campbell: I'll Be Me, about Campbell's extraordinary life and career, as well as his disease, was released. The film's theme song, "I'm Not Gonna Miss You," co-written and sung by Campbell, won a Grammy for Best Country Song, and both the movie and its soundtrack received numerous other accolades. I'll Be Me was also a finalist for the prestigious Peabody Awards.

Campbell died on Aug. 8, 2017.

7 Songs You Didn't Know Glen Campbell Played On

Glen Campbell's name is legendary in country music thanks to his iconic hit songs, but he's also a major figure in music as a whole due to his crossover hits and, especially, because of his work as a session musician. Whether fans know it or not, Campbell left his mark on myriad songs in the 1960s, before and as he was starting his solo career.

When Campbell moved to Los Angeles in 1960, he got a job as a writer and demo singer / player for a publishing company; that led to work as a session musician. Campbell became part of the Wrecking Crew, an in-demand group of session players who worked on songs for everyone from Sonny & Cher to Frank Sinatra. They were producer Phil Spector's go-to house band, but were sometimes uncredited players; the late Leon Russell was also a member.
Flip through the photo gallery below to learn more about Campbell's work as a session musician -- specifically, about seven hit songs that, fans may not know, include his playing:

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