G8 'will develop dementia cure or treatment by 2025'
Leading nations have committed to developing a cure or treatment for dementia by 2025 at the G8 dementia summit.
Health ministers meeting in London said it was a "big ambition" and that they would significantly increase funding for research to meet that goal.
The UK has already said it aims to double its annual research funding to £132m by 2025.
The global number of dementia sufferers is expected to treble to 135m by 2050.
The G8 said it would "develop a co-ordinated international research action plan" to target the gaps in research and ways to address them.
Dementia across the globe
44 millionglobally have dementia
135 millionwill have the disease in 2050
By then71%will be poor and middle income
$600bnglobal cost of dementia
In the UK, cancer research gets8xas much funding as dementia
It also called on the World Health Organization to identify dementia as "an increasing threat to global health" and to help countries adapt to the dementia timebomb.
In a statement it said "We recognise the need to strengthen efforts to stimulate and harness innovation and to catalyse investment at the global level."
Dementia is incurable and ultimately leaves people needing full-time care as brain function wastes away.
There is growing concern that some countries will simply not cope with the growing burden of dementia.
It costs the world billions of dollars each year: £370bn ($604bn) in 2010, according to the World Health Organization.
Health ministers from the G8 nations are meeting - under the presidency of the UK - to find the best ways to advance research.
David Cameron called on governments, industry and charities all to commit more funding. He said the G8 should make this the day "the global fight-back really started".
He said the UK Government would boost annual research funding from £66m, the 2015 pledge, to £132m, which will be adjusted for inflation, by 2025.
Mr Cameron told the summit: "This disease steals lives, wrecks families and breaks hearts."
"If we are to beat dementia, we must also work globally, with nations, business and scientists from all over the world working together as we did with cancer, and with HIV and Aids.
"This is going to be a bigger and bigger issue, the key is to keep pushing."
The health secretary Jeremy Hunt said: "The amount [of money] going into research is too little.
"We would like a cure to be available by 2025. It's a big, big ambition to have. If we don't aim for the stars we won't land on the moon."
However, so far only the UK has made a definite funding announcement with the other nations committing to "a significant increase in overall dementia research".
Mr Hunt said a Dementia Envoy would be appointed that would also help industry and charities boost funding.
The chief executive of the Alzheimer's Society, Jeremy Hughes, said: "Today the UK has demonstrated global leadership on tackling dementia.
"Dementia has come out of the shadows and is centre stage - but we must ensure G8 has a lasting legacy.
"The governments' have all committed to updating progress on research biannually, but every month counts for the millions of people living with dementia worldwide."
Hilary Evans, from the charity Alzheimer's Research UK, said: "This action plan is the best possible news for people living with dementia, it tells them that the world will fight for them, and that the best and most collaborative science is our greatest weapon.
"With the right investment, we can be more optimistic than ever that we will meet if not exceed the G8's 2025 target."
A dementia brain scan will also be introduced for some NHS patients with complicated symptoms.
It could help rule out Alzheimer's disease, the most common form of dementia, by hunting for damaged proteins in the brain.
A radioactive marker which binds to amyloid, a hallmark of Alzheimer's disease, will be injected. If there is amyloid in the brain then the tracer will show up on brain scans.
The test will initially be offered at Imperial College Healthcare NHS Trust in London and will be rolled out to other specialist centres.
Dr Richard Perry, a consultant neurologist at Imperial, told the BBC: "For a patient who can't get an answer using the usual tests this will make a big difference as it'll provide clarity.
"Knowing the cause is the first step to getting treatment."
Around 100 patients a year are expected to get access to the scan.
There have been a flurry of other funding announcements tied to the talks including:
- The Medical Research Council (MRC) will commit £50m to improve treatments and delay the progression of the disease
- The Alzheimer's Society has promised to spend at least £100m on research in the next decade
- A new £3m "Dementia Consortium" will unite the charity Alzheimer's Research UK, two pharmaceutical companies and MRC Technology in the hunt for new drugs
- The Engineering and Physical Sciences Research Council has put up £5m improve ways of diagnosing and measure disease progression.
Meanwhile, the Care Quality Commission (CQC) plans unannounced inspections of the care of dementia patients at 150 institutions across England.
The CQC said it would look at what needed improving, how to cut hospital admissions from care homes and ways to help people with dementia maintain their physical and mental well-being.
David Behan, chief executive of the health regulator, said: "We know that these people are often vulnerable because of their condition and can rely on a number of services across health and social care to support their physical, mental and social well-being.
"Our findings will draw conclusions on a national scale about what works well and where improvements are required."
A national report on the issue will also be published in May.