Tony Bennett was diagnosed with Alzheimer's disease in 2016.
The 94-year-old's condition was shared on Monday by AARP, a US campaign group on age-related issues.
AARP said the singing legend, who was born Anthony Dominick Benedetto, was diagnosed with the disease, which affects memory and cognitive functions, more than four years ago.
Gayatri Devi, the neurologist who diagnosed the singer, told AARP that Bennett had “cognitive issues, but multiple other areas of his brain are still resilient and functioning well".
“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," she said.
Bennett shared the article from the group’s magazine to Twitter, writing: “Life is a gift – even with Alzheimer’s. Thank you to Susan and my family for their support, and @AARP The Magazine for telling my story.”
Life is a gift - even with Alzheimer’s. Thank you to Susan and my family for their support, and @AARP The Magazine for telling my story.
Read more here:https://t.co/R05A4jc5BF⁰
📸 Kelsey Bennett pic.twitter.com/ApxBCpGv0y
— Tony Bennett (@itstonybennett) February 1, 2021
AARP said Bennett had so far been "spared" the symptom of disorientation, which can lead some sufferers to wander from their homes, "as well as the episodes of terror, rage or depression that can accompany Alzheimer’s’ frightening detachment from reality".
However, it said "there was little doubt that the disease had progressed" as “even his increasingly rare moments of clarity and awareness reveal the depths of his debility”.
Bennett is set to release a follow-up to his 2014 Cheek To Cheek collaboration with Lady Gaga in spring. The pair recorded the songs between 2018 and 2020.
The 18-time Grammy winner has been supported by his wife Susan, whom he married in 2007.
He has two sons from his first marriage, to Patricia Beech, sons Danny, 66, and Dae, 65, and two daughters from his second marriage, to Sandra Grant: Antonia, 46, and Joanna, 50.
With additional reporting by PA.
Watch: Tony Bennett reveals diagnosis of Alzheimer’s disease