A drug called Aricept has rejuvenated the brain of a 70-year old woman, leading scientists to believe that the illness can be reversed. Researchers found that areas of the brain governing the short-term memory were revived. Scans had shown that these areas had been shut down by the onset of Alzheimer's.

However, after four months of treatment, the woman regained her memory and speech and find her way around. More scans showed that the brain cells that doctors thought were dead, were actually lying dormant and the drug switched them back on.

Research leader Dr Paul Kemp of the University of Southampton (UK) said 'It was a dramatic improvement - the Lazarus effect.' Alzheimer's affects 50,000 people in Britain.

Dr Kemp does not think that the drug is a cure for the disease but it may delay its worst effects. 'Eventually, sufferers will die with the disease rather than of the disease. They will live so long they will die of something else.'