Dementia now costs the UK economy twice as much as cancer but gets a fraction of the funding to find causes and cures, a report seen by the BBC shows.
For every one pound spent on dementia research, 12 times that sum goes on investigating cancer, figures from the Alzheimer's Research Trust indicate.
Bridging this gap is urgent, it says, particularly given the numbers with dementia are much higher than thought.
With 821,884 sufferers, dementia costs the UK £23bn annually, the report says.
The number of sufferers is 15% higher than had been estimated, according to the Dementia 2010 Report , and the trust says it will now pass the one million mark before 2025.
The annual burden on the economy meanwhile is 35% higher than the previous calculations of £17bn.
Researchers from the University of Oxford compared the cost of caring for a person with dementia to the cost of dealing with cancer, heart disease or stroke - the three main causes of death in the UK.
Shouldering the burden
As well as immediate health care expenses, they looked at the costs of social care, unpaid carers and productivity losses.
Every dementia patient, they found, costs the economy £27,647 each year - nearly five times more than a cancer patient, and eight times more than those with heart disease.
It was the costs met by unpaid carers and incurred by long-term institutional care - rather than expenses shouldered by the NHS - that pushed up the burden of dementia.
But they also found that the costs of these conditions appeared to bear little relation to the respective amounts invested by government and charities in research into causes, treatment and prevention.
With nearly £600m a year, cancer research funding was 12 times that of the £50m devoted to dementia, while heart disease received three times as much. Only stroke research received less.
They calculated that for every person with cancer, £295 is spent on research, compared with just £61 for each person with dementia.
Donation dilemma
The researchers believe the fact that a larger proportion of the cost of caring for cancer and heart disease falls on the NHS, rather than the individual and their family, goes some way to explaining the discrepancy in government funding for research.
Cancer and heart charities have also tended to be larger than those devoted to dementia.
But our own perceptions of this disease - one which primarily strikes in old age - may influence what we are prepared to donate, the researchers suggest.
"Many of us know people who have had cancer or heart disease but have been successfully treated and survived, so there is a perception that something can be done, and that more research will allow even more to be done," says Alastair Gray, professor of health economics at the University of Oxford and author of the report.
"In contrast there are no cures for dementia at present; there are not even many ways of delaying it or slowing it down, so there may well be a feeling of inevitability surrounding it. However the lack of effective treatments is surely an argument for devoting more effort to research, not less."
Rebecca Wood, head of the Alzheimer's Research Trust, said the true economic impact of dementia "had been ignored for too long. This report shows that dementia is the greatest medical challenge of the 21st Century".
"If research leads to a cure for Alzheimer's and other dementias, annual saving to the UK economy would be equivalent to hosting the London Olympics twice, or funding every British university for three years."
Michelle Mitchell, charity director for Age Concern and Help the Aged, said the disease was not going to go away and it was of "paramount importance" that the research was funded now.
Andrew Ketteringham, of the Alzheimer's Society, said: "We've got a lot of catching up to do and a lot of investment to do. And if people say, 'Well, how can we afford that?', I say, 'Well, we can't afford not to do that.'
"If we could just delay the onset of dementia by five years, we'd be able to save huge amounts."
But Care Services Minister Phil Hope said that by next year the government would be investing nearly £1bn in health research. "This money is awarded to the best quality research for any health condition, including dementia.
"I have set up a new ministerial group which will drive forward research into the causes, cure and care of dementia and help dementia researchers get more access to funding. This group will hold its first meeting later this month.
"I have also just appointed a new National Clinical Director for
Dementia, Professor Alistair Burns, to provide leadership across the whole
dementia strategy and help bring up standards of
dementia care across the country.
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