Researchers in London are working on a way to prevent Alzheimer's before it even starts. Two hundred people are taking part in a new trial, which will allow scientists to detect subtle changes in brain chemistry, before the physical symptoms of the disease appear.
Those taking part have a rare genetic mutation, which means they have a 50/50 chance of developing the disease early in life - typically in their 30s or 40s.
Lead UK researcher Dr Cath Mummery from University College Hospital in London, told BBC News: "They know that they may get Alzheimer's disease because they may have a mutation that causes it, but they don't have symptoms. So we're trying to prevent the onset of the disease which is very different."
The international study, run by the Dominantly Inherited Alzheimer Network Trials Unit, is the first of its kind.
Scientists will be monitoring patients' cognitive performance and brain and spinal fluid, looking for subtle changes which can be detected years before bodily symptoms appear.
At the same time, they will be testing two immunotherapy drugs to see if they can stop the disease in its tracks.
The knowledge gained from the trial could help develop new preventative treatments not only for those with rare genetic forms of Alzheimer's, but for everyone affected by the disease.