Tragic former AC DC star Malcolm Young underwent heart and lung operations just before dementia forced him to quit the band, according to his brother Angus.

The bassist stepped down from the group in September (14) after his family confirmed his mental issues had robbed him of his musical talents.

Brother Angus Young now reveals he was also dealing with some physical ailments, but he has since recovered from them.

He tells radio station Kisw, "He had a lung operation; he had a heart operation. He seemed to get everything hit him at once, besides his dementia. So he had quite a lot of things going on.

"The physical side of him is great, because he got the best treatment for his lungs and for his heart. At the moment, he's in good care. He's happy himself, because he's being well looked after."

Guitarist Angus and frontman Brian Johnson recently revealed their ailing bandmate's dementia issues started becoming a problem during Ac Dc's last world tour, which ran from 2008 to 2010, and there were times he didn't know where he was.

Johnson said, "God knows what went through his mind in some nights when he wasn't that well. He'd go onstage and... 'Oh s**t!' Can you imagine knowing you're not sure about (what's happening)? You know where you are, put it that way, but your mind's playing tricks."