Windsor, who is best known for playing EastEnders favourite Peggy Mitchell, was diagnosed with the condition in 2014.
Appearing on Good Morning Britain on Thursday (22 October), Kemp, who played Windsor’s son Grant on the long-running BBC soap, told fans that while she had recognised him during a recent video call, he wasn’t hopeful about her overall progress.
"I spoke to her on Sunday on FaceTime with her husband Scott,” he said.
“She recognised me, but we have to be realistic that there is no cure for Alzheimer's. It's probably not going to get much better for her.”
In June, Kemp presented a two-part documentary titled Ross Kemp: Living With Dementia based on his friendship with Windsor, during which he recalled the first time the 83-year-old actor had been unable to recognise him.
“I’ve been friends with Barbara and Scott for 25 years,” he said. “I see her as often as I can – every couple of months before the lockdown – and the deterioration in her condition has been shocking and to those of us close to her, deeply upsetting.”
In August, Windsor was moved to a care home due to the worsening of her health, with her husband saying that he made the decision after being advised by her neurologist.