More than 520,000 Britons have Alzheimer's - the most common form of dementia, which is the leading cause of death in UK.

A study in the Lancet looked at whether a blood test could indicate the most common form of dementia and diagnose people decades before symptoms are clear enough to be identified…

More than 520,000 Britons have Alzheimer's - the most common form of dementia, which is the leading cause of death in UK.