Once, I knew a doctor, a man prominent in his profession, a man distinguished in his service in the British army in the Second World War. Captured at the fall of Singapore, he had acted as medical officer in the prisoner of war camp in which he was held, working without proper medication or equipment. When the camp had been liberated, he had weighed just five stones.

A well-known consultant physician, he had continued to see private clients until he was in his 80s. At the age of eighty-five, he received a diagnosis of cancer with complete equanimity. “What of it?” was his response to those who expressed concern about his health. He chose to have neither intervention or treatment. Despite his age, he was leading a full and active life, caring for himself in his substantial house, driving his car to the shops and on visits to his friends.  After his death, a family member told me that the thing the man most feared was dementia and that the illness had ensured that dementia, if it arrived, would never have the opportunity to develop.

It was a decision that gave great cause for pondering, a man who had seen humanity at its worst, who had endured the most abominable physical and psychological conditions, had come through these things; his fear was not of anything that might happened in the world he inhabited, but what might happen within his brain.

On this evening’s BBC news there was a report that, “people keep making new brain cells throughout their lives (well at least until the age of 97), according to a study on human brains”. The  report includes comments from Dr Rosa Sancho, the head of research at Alzheimer’s Research UK, who said, “While we start losing nerve cells in early adulthood, this research shows that we can continue to produce new ones even into our 90s . . . Alzheimer’s radically accelerates the rate at which we lose nerve cells and this research provides convincing evidence that it also limits the creation of new nerve cells.”

If dementia accelerates the loss of existing cells and inhibits the creation of new ones, then the answer will lie in finding a way to ensure that production exceeds reduction. Research has not been successful – thus far. The breakthrough, when it comes, will be one of the greatest revolutions in medicine. Perhaps not an elixir of eternal youth, it will allow lives of quality in old age, it will lift a huge burden from the care budget, and it will take away the fear.