A majority of Australians say they don't know what to say to a person with dementia, a survey shows, despite 436,000 people living with it.

More than half of Australians feel they do not know what to say to a person with dementia, new research has revealed.

That comes despite 436,000 Australians living with the condition and an extra 250 being diagnosed with it every day.

A survey of 1500 people, commissioned by Dementia Australia, shows four in five people also think others feel uncomfortable around those with the brain disorder.

About 60 per cent of people said they didn't know what to say with someone with dementia and half were worried they wouldn't be understood, may say the wrong thing, or hurt the person's feelings.

Dementia Australia chief executive Maree McCabe says the insights are "a real wake up call", given dementia impacts so many Australians.

"The way we respond, communicate and interact with a person with dementia has an enormous impact on their day to day life," she said.

"We can all do more to make sure people living with this disease remain included and accepted in their own community."

Ms McCabe has encouraged people to complete a short online course on the Dementia Australia website to boost their understanding.

But she has been encouraged by the number of people surveyed who were aware of dementia.

About 80 per cent said they'd heard of it and 75 per cent were able to identify basic facts about it.

The brain disorder is the second-leading cause of death among all Australians, claiming more than 13,000 lives a year.

The number of Australians with dementia is expected to hit 590,000 in a decade and almost 1.1 million by 2058.