The 81-year-old actress played Basil Fawlty's wife Sybil in the BBC series.
Timothy West - who recently joined the 'EastEnders' cast - opened up about his wife's condition in the More4 documentary, 'Great Canal Journeys', which sees them navigate Britain's canals on a slow boat.
He says: “She can’t remember things very well, but you don’t have to remember things on the canal.
“You can just enjoy things as they happen — so it’s perfect for her.”
The actress, who is still getting roles, says her condition won't keep her from the stage.
“I always say I want to die on the eighth curtain call.
“Eight will mean the show’s been rather a success. I just hope I’m somewhere near the middle and have been reasonably good in the part.”
Alzheimer’s Society’s director of external affairs, Dr Alison Cook, said: “Alzheimer’s Society would like to thank Timothy West for speaking out about his wife Prunella Scales’ dementia and raising awareness of the condition.
“Their recent adventure navigating Britain’s canals shows that it is possible to live well with dementia and plan to carry on enjoying life.
“We would urge anyone who is concerned about themselves or a loved one to speak to their GP today or contact Alzheimer’s Society for advice and support.”
Rebecca Wood, Chief Executive of Alzheimer’s Research UK, says:
“It’s always sad to learn that a much-loved public figure is living with Alzheimer’s, and this news will have touched the hundreds of thousands of families across the UK who are facing a similar struggle. By speaking out about their experiences, the couple have helped bring dementia into the spotlight, in turn helping to tackle some of the stigma that still surrounds the condition. We are grateful to them for helping to bring attention to the many challenges faced by people with Alzheimer’s disease.
“Timothy West has backed our calls for increased funding for dementia research in the past, and research is vitally important to bring about better outcomes for people with the condition. Though we currently lack treatments that can stop the diseases that cause dementia, with the right backing, research can deliver new treatments that are so desperately needed.”