Symptoms can include memory loss and difficulties with thinking, problem-solving and language. It occurs when the brain is damaged by afflictions such as Alzheimer's disease or stroke.
"As an increasing number of people are diagnosed with dementia more people are seeing the profound impact that it can have on both the individual as well as the wider family," said Paul Green, director of communications at over-50s company Saga, which conducted the survey.
"However, while these fears are completely understandable, it's important that education around the condition is enhanced to give a greater understanding of the benefits of early diagnosis - and how this can help those living with the condition continue to lead fulfilling lives."
Commenting on the poll Hilary Evans, director of external affairs at charity Alzheimer's Research UK, said: "It's no surprise to learn that fear of dementia in people over 50 is high: dementia affects over 820,000 people in the UK and we currently lack treatments to tackle the condition.
"The challenge is to find new ways to treat and prevent dementia to show there is hope of taking on dementia and beating it.
"Research holds the answer to this devastating condition, and with the number of people affected set to grow as the population ages, the need for investment in research has never been more urgent."
Alison Cook, director of external affairs at the Alzheimer's Society charity, said: "The possibility of losing the very essence of what makes you the individual that you are is a frightening prospect.
"But fear can mean people don't get a diagnosis and can often miss the opportunity to access treatments (which are only effective for people in the earlier stages of the condition) and the time to make important decisions about their future.
"We urge anyone concerned about dementia to speak to their GP and get in touch with Alzheimer's Society, as there are lots of ways we can help."
- AAP
