We don't know the cause, there is no treatment or cure, and it is fatal. Dementia is the health challenge of this generation.
To mark Dementia Awareness Week, Claudia Hammond investigates this complex group of brain diseases that progressively lead to the death of brain cells and affect memory and behaviour.
She finds out how UK scientists are some of the global leaders in the field of dementia research. She talks to Professor Julie Williams about her pioneering work in genetics, to Simon Lovestone about his team's search for a biomarker in blood and finds out about the drugs in the developmental pipeline which could, for the first time, treat the underlying disease itself.
Claudia asks why the quality of dementia care in the UK remains in the bottom third of the whole of Europe and questions what improvements patients and their carers can expect from the new National Dementia Strategy.