Tony Bennett doesn't know he has Alzheimer's disease.

The music legend's wife, Susan Crow, has opened up about her husband's battle with the illness – which slowly destroys memory and thinking skills – and revealed he is not aware he is suffering and has moments where he is "more alert".

In an interview with Anderson Cooper on CBS News' 60 Minutes, Susan said: "Every day is different. Tony late at night, sometimes early in the morning, he's more alert, if I can use that word.

"So, I'll tell him, "Tone, you're gonna be on 60 Minutes.' He's, like, "Great.' I said, "You remember that show, 60 Minutes he's, like, "I do.' But in any other given moment, he won't know."

She then said: "He recognizes me, thank goodness, his children you know, we are blessed in a lotta ways. He's very sweet. He doesn't know he has it."

Anderson clarified: "He doesn't know he has it?" to which Susan confirmed: "No."

The legendary singer was diagnosed with Alzheimer's in 2016, and the I Left My Heart in San Francisco star recently retired from performing and released his final album, Love for Sale, a collaborative LP with Lady Gaga, last week.