The discovery raises the prospect of giving people drugs in the very earliest stages , when it is easiest to treat , and even stopping the disease in its tracks ( file image ) The telltale signs of Alzheimer ’ s can be seen in people as young as 20 , research shows . The ‘ unprecedented ’ finding suggests that the disease starts to eat away at the brain half a century before symptoms develop . This is a ‘ much younger age than the scientists ever imagined ’ . The discovery raises the prospect of giving people drugs in the very earliest stages , when it is easiest to treat , and even stopping the disease in its tracks . However , British experts cautioned that the research is still at an early stage . Crucially , it isn ’ t known how many people who have the early signs of Alzheimer ’ s in their brains in their 20s will go on to develop the disease . Alzheimer ’ s and other forms of dementia affect more than 800,000 Britons and , worldwide , the number of sufferers is predicted to treble to 44million by 2050 as the population ages . With no cure for dementia and existing drugs of limited use , the Prime Minister David Cameron has described dementia as ‘ the key health challenge of this generation ’ . Researchers , from Northwestern University in Chicago , examined the brains of elderly people with and without Alzheimer ’ s , as well as samples taken from 13 people aged between 20 and 66 . These younger people were free of memory problems when they died . Tests showed that beta-amyloid , the toxic protein that clogs up the brain in Alzheimer ’ s , had started building up in people as young as 20 . It had been thought that the damage to the brain started just 15 or 20 years before the disease takes hold . Lead researcher Professor Changiz Geula said : ‘ Discovering that amyloid begins to accumulate so early in life is unprecedented. ’ The amyloid clumps were found inside neurons , or brain cells , that are involved in memory and attention and are among the first to die in normal ageing , as well as in Alzheimer ’ s . The professor said : ‘ This points to why those neurons die early . The lifelong accumulation of amyloid likely contributes to the vulnerability of these cells . ‘ The growing clumps likely damage and eventually kill the neurons. ’ Scientists around the world are trying to make drugs that stop Alzheimer ’ s in its tracks . They believe the key to treatment will be to give the medicines as early as possible in the disease . But doctors called for more research to be carried out with not everyone who showed signs of Alzheimer 's developing the disease . Even delaying the onset of Alzheimer ’ s would have a massive impact on the lives of sufferers and their loved ones . The Alzheimer ’ s Society gave the research , which is published in the journal Brain a cautious welcome . Dr James Pickett , the charity ’ s head of research said the study was very small and that it is already known that not everyone with amyloid clumps will develop Alzheimer ’ s . He added : ‘ More research is needed to explain why only a proportion of people with a build-up of amyloid go on to develop Alzheimer ’ s disease . ‘ There are clinical trials currently underway of drugs that reduce amyloid in the brain and we hope to find out if this is a successful way to prevent or delay Alzheimer ’ s disease in the next few years. ’ Dr Laura Phipps of Alzheimer ’ s Research UK , said : ‘ With half a million people living with Alzheimer ’ s in the UK and that number on the increase , we urgently need new treatments to stop the disease in its tracks . ‘ A greater understanding of the early stages of Alzheimer ’ s could provide new clues to help fight the disease , which is why investment in research is crucial . ’
Discovery means people can be treated years before showing symptoms . Tests showed toxic protein which clogs brain started growing at age 20 . Comment: This explains why Alzheimer 's can advance so quickly , said experts .