Scott Mitchell, 56, said the ex-EastEnders and Carry On star, 82, often asks where he lives and does not know who he is.
He told the Sunday Mirror that the actress "still has the most wonderful sense of humour" and "we can still make each other laugh".
But he said: "I've definitely seen a progression in the last year. Barbara's symptoms have deepened, especially where her confusion is concerned.
"Constantly, she does not realise where we are, even in the house. She will ask me, 'When are we going home?"'
The star regularly thinks that her parents are still alive.
"Barbara will often say to me, 'Do you know how to get in touch with my mum? I'd like to have a chat with her. I haven't seen her for ages, I need to see her,"' Mitchell said.
"It's heartbreaking. They are very difficult situations to be faced with."
He said: "I have to remember she doesn't always realise it's me. Sometimes she will say, 'Where is Scott? Do you know where my husband Scott is?"'
Dame Barbara was diagnosed in 2014 and Mitchell has been campaigning to raise more awareness about Alzheimer's.
The actress delivered a letter to Prime Minister Boris Johnson last year to call for better care for fellow sufferers.