A global survey exploring attitudes about dementia has found two-thirds of people think it's a natural part of ageing rather than a medical condition.

It's one of the world's fastest growing causes of death but stigma and misunderstandings still surround dementia.

The world's largest dementia survey by Alzheimer's Disease International suggested the stigma associated with dementia was similar to that of mental health, which discourages people from seeking help.

"Stigma is the single biggest barrier limiting people around the world from dramatically improving how they live with dementia," Alzheimer's Disease International's chief executive Paola Barbarino said.

"Stigma can undermine life goals and reduce participation in meaningful life activities as well as lower levels of well-being and quality of life."

The report surveyed 70,000 people across 155 countries, including Australia, and found two thirds of people believe dementia is a natural part of the ageing process when it is actually a medical condition.

Additionally, one in five people people attribute dementia to bad luck, almost 10 per cent to God's will and two per cent to witchcraft.

The survey showed 62 per cent of healthcare practitioners assume it is normal part of ageing and around 50 per cent of people living with dementia feel ignored by doctors and nurses.

Forty-eight per cent of respondents believe the memory of a person with dementia will never improve, even with medical support, while one in four people think there is nothing we can do to prevent dementia.

Ms Barbarino says these are major barriers against people seeking support and that talking and planning can help people to live well with dementia for as long as possible.

"Evidence suggests that when people living with dementia and their families are well prepared and supported, initial feels of shock, anger and fried are balanced by a sense of reassurance and empowerment," she said.

The number of people living with dementia is predicted to more than triple to 152 million by 2050, with Alzheimer's disease and other dementias the fifth most common cause of death globally.

In 2019, Dementia Australia says there are an estimated 447,115 Australians living with dementia. The number of people with dementia is expected to increase to an estimated 589,807 by 2028 and 1,076,129 by 2058.

It's hoped the findings of the survey will lead to positive reform and change across the world.

Analysis of the study was carried out by the London School of Economics and Political Science.

* World Alzheimer's Day is on Saturday, September 21