Former Germany striker Gerd Mueller "is slowly passing to the afterlife in his sleep," his wife Uschi said before celebrating his 75th birthday on Tuesday.

'The Bomber' Mueller, who won the World Cup in 1974 and countless domestic and European titles with Bayern Munich, suffers from dementia and lives in a specialized care home.

"He spends almost 24 hours a day in bed. He has just the rare moments of being awake," she told newspaper Bild in an article published on Monday.

"It's beautiful when he opens his eyes a little bit. Sometimes he manages to say yes or no with his eyes.

"He's calm, peaceful, I don't think he's suffering and is slowly passing to the afterlife in his sleep," she added.

Mueller, who also lifted the European Championship with his country, holds the record of 40 goals in one Bundesliga season, set in 1971/72.

"It's thanks to his goals that Bayern Munich rose to the international level and are there today," his former team-mate Franz Beckenbauer said.

"In my eyes he is the most important player in Bayern Munich's history. I'm sure people will still talk about Gerd Mueller in 100 years."