Tony Bennett has been diagnosed with Alzheimer’s disease, his wife, Susan, told AARP The Magazine.

According to his family, the 18 time GRAMMY winner is taking each day one note at time. Bennett’s greatest therapy is singing. He rehearses twice a week.

“He has devoted his whole life to the Great American songbook and now the songbook is saving him,” Susan Bennett told CBS This Morning.

Alzheimer’s is a degenerative brain disease characterized by progressive memory loss that affects speech, understanding, and recognition of family and friends.

More than five million Americans are living with Alzheimer’s, according to the Alzheimer’s Association, including one in 10 people age 65 or older.

There’s research suggesting a link between diabetes and Alzheimer’s, suggesting that people with diabetes, especially type 2 diabetes, are at higher risk of eventually developing Alzheimer’s dementia or other dementias.

Alzheimer’s symptoms may initially include repeating questions, getting lost in a familiar place or misplacing things, and may eventually progress to hallucinations, angry outbursts, and the inability to recognize family and friends or communicate at all. Alzheimer’s has no cure.

Tony Bennett, first diagnosed in 2016, has so far been spared the disorientation and the episodes of terror, rage  and/or depression.

Susan Bennett said that he can still recognize family members, but the magazine reported that “mundane objects as familiar as a fork or a set of house keys can be utterly mysterious to him.”

His diagnosis hasn’t stopped him from performing. According to People Magazine the 94 year old singer has has concert dates scheduled for later this year, with the first in March.

“It kept him on his toes and also stimulated his brain in a significant way,” Bennett’s neurologist, Gayatri Devi told AARP The Magazine. “He is doing so many things, at 94, that many people without dementia cannot do. He really is the symbol of hope for someone with a cognitive disorder.”

“He’s not the old Tony anymore,” his wife, Susan, said. “But when he sings, he’s the old Tony.”

Bennett’s family kept his secret for four years, but decided to break their silence now with the release of his new album. The disclosure is a way to remove some of the stigma associated with the incurable disease, they said.

“Being open about a diagnosis in such a public manner takes great courage and compassion,” said Beth Kallmyer, vice president for care and support with the Alzheimer’s Association.

Editor’s note: It has not been reported that Tony Bennett is living with diabetes.