Dr Norman Swan reports on "Holding on to Hope", looking at lifestyle choices whch may help delay the onset of dementia."It's the number one fear that older people have. More than any other disease … more than anything else." (Dementia clinician)Half a million Australians live with dementia and for the past two decades scientists have been working on a new drug treatment they hope will combat the most common form, Alzheimer's disease."If we can give people another five years of quality life, that's going to make a massive difference to people around the world. It's going to make a massive difference to healthcare systems around the world as well." (Neurologist)ABC's health expert Dr Norman Swan investigates the science behind the treatment in the race to solve dementia.