Watch the report by Richard Slee below...
It's a terrible disease which affects hundreds of thousands of people, but what is often overlooked is that many younger people also suffer symptoms of dementia.
About five per cent of sufferers are classed as having 'early onset' dementia - but the figure could be much higher because of difficulties diagnosing the condition.
That was the case with Robin Witt from Bournemouth, who was eventually diagnosed at just 42 years old. Richard Slee reports.
Fred talks to Kelly Inwood, area Manager for the Alzheimers Society in the South West