Singer Glen Campbell has died, aged 81.

The Wichita Lineman hitmaker, who released his final album, Adios, earlier this year (17), had been battling Alzheimer's disease for years before his death on Tuesday (08Aug17), and his family admitted him to a hospice last year (16) when he became a danger to himself and others.

Speaking of his battle with the memory robbing condition in June, 2016, his wife Kim confessed the country legend had lost the ability to speak and no longer recognised family members.

"He is content and cheerful...," Kim, his wife of 35 years, told U.S. news show Access Hollywood Live. "He's kinda in his own little world but he sings to himself a lot.

"He has complete aphasia; he doesn't understand language and he can't communicate verbally. But he understands the universal language of love and smiles and kisses and hugs... And he enjoys dessert."

The Rhinestone Cowboy singer was diagnosed with Alzheimer's in 2011 and continued touring until 2014, when he was moved into a long-term care community near his Nashville, Tennessee home.

Campbell's career spanned six decades and he sold over 45 million records.

Born in Billstown, Arkansas, Glen was one of 12 kids in a sharecropping family. He picked up the guitar as a child and became a big fan of jazz musician Django Reinhardt.

Campbell dropped out of school at the age of 14 and moved to Wyoming to perform with a musician uncle. He moved to Los Angeles and became part of session group the Wrecking Crew, performing on hits like the Byrds' Mr. Tambourine Man, Elvis Presley's Viva Las Vegas, and You've Lost That Lovin' Feeling by the Righteous Brothers.

In 1964, Campbell stood in for Brian Wilson after he suffered a nervous breakdown on tour with the Beach Boys.

He found solo success thanks to encouragement from Wilson with a cover of Buffy Sainte-Marie's Universal Soldier, and scored a massive hit in 1967 with songwriter Jimmy Webb's By the Time I Get to Phoenix.

The two also collaborated on Galveston, Gentle on My Mind, and Wichita Lineman, which was Campbell's first top 10 hit.

In 1968, Campbell guest hosted the Smothers Brothers Comedy Hour and he was such a hit he landed his own variety show, The Glen Campbell Goodtime Hour, which he hosted from 1969 until 1972.

Glen also found fame as a movie star after John Wayne cast him in cowboy classic True Grit.

But his run of good luck ran out in the early 1970s as the hits dried up and his show was cancelled. He bounced back in 1975 with Rhinestone Cowboy, the song that was to become his signature tune.

Campbell, who was married four times, struggled with alcoholism and cocaine addiction throughout the late 1970s and 1980s - and he was arrested in 2003 for a hit-and-run incident. The singer pleaded guilty to leaving the scene of an accident while drunk, and spent 10 days in jail.

Campbell was inducted into the Country Music Hall of Fame in 2005.