Half of UK adults cannot identify any key risk factors for dementia, according to a study by Alzheimer's Research UK.
The charity surveyed 2,361 people and found that only 1% were able to name the seven known risk or protective factors for dementia.
The six risk factors are heavy drinking, genetics, smoking, high blood pressure, depression and diabetes.
Physical exercise is a protective factor against the disease.
The study, entitled Dementia Attitudes Monitor, found that more than half of UK adults now know someone with dementia.
But only half recognised that dementia is a cause of death, and they found that a fifth incorrectly believe it is an inevitable part of getting older.
Although a third of cases of dementia are thought to be influenced by factors within our control, only 34% of people surveyed believe it is possible to reduce the risk of dementia, compared with 77% for heart disease and 81% for diabetes.
Hilary Evans, chief executive of Alzheimer's Research UK, said that despite growing dementia awareness, there was still a lot of misinformation.
"It is a sad truth that more people are affected by dementia than ever before and half of us now know someone with the condition," she said.
"Yet despite growing dementia awareness, we must work harder to improve understanding of the diseases that cause it."
- More than 850,000 people in the UK are living with dementia.
- This number is set to rise to more than one million by 2025.
- Dementia is an umbrella term for a set of symptoms that affect cognitive function, such as memory loss, confusion and personality change, which get worse over time.
- Alzheimer's disease is the most common cause of dementia, accounting for approximately two-thirds of all cases.
- An individual's risk of developing dementia is made up of different factors including age, genetics and lifestyle.
Source: Alzheimer's Research UK
Sue Strachan is 63 and lives in Herefordshire. She was diagnosed with vascular dementia in 2014.
"I wasn't very fit when I was diagnosed with dementia and my GP advised me to take up exercise to try to manage my condition," she said.
"I do wish I'd started earlier, because good heart health can have such a positive impact on the brain. I can see that society's view of dementia is improving, but I still experience misunderstanding about the condition - not least that there's nothing that can be done to help."
Sue ran last year's London Marathon for Alzheimer's Research UK to help raise awareness.
The charity said reducing the number of people who believe that dementia is an inevitable part of ageing is "key", as "this belief drives other negative attitudes towards dementia".
"Our findings show that those who believe dementia is an inevitable part of ageing are less likely to see the value in seeking a formal diagnosis, and are less likely to engage with research developments that could bring about life-changing treatments and ultimately, a cure."
The study found key groups of people whose understanding of dementia is lower, including those from black, Asian and minority ethnic backgrounds, and adults under 24 and over 65.
There is not currently a test for dementia, but the survey found that if there was a breakthrough in research, 85% would be willing to take a test through their doctor before symptoms showed.