Dr Gillings, appointed by David Cameron to create the global council in 2013, said “great strides” had been made in improving scientific understanding of dementia and of the gaps in research.

“The original goal [of the council] was disease modification by 2025,” he said. “I feel a lot more optimistic now: I wouldn’t be surprised if we get there by 2020 or 2021.”

Dr Gillings said scientists were increasingly of the view that it had been a mistake to treat dementia as one type of disease, saying that it was likely that breakthroughs would come from developing treatments which were targeted at different subtypes of the condition.

“We may need more customised diagnosis,” he said. “We used to just think cancer now we know there are many different types, with different treatments. We need to approach dementia similarly.”

Currently the only medication available for diseases such as Alzheimer’s can mask symptoms but not delay the onset of disease.

Dr Gillings said progress was being made developing treatments which could remove the plaques in the brain which are a hallmark of the disease.

Such treatments might halt or reverse the progress of dementia, he said, with some kind of brain training used to help rebuild lost neural pathways.

Other types of patients might benefit from treatments which “untangle some of the neural tangles” which might enable regeneration, he said. Saluting recent British investment in science, and the creation of a £150m Dementia Research Institute, he said that nonetheless, breakthroughs were more likely in the United States, which ploughed far more into Research and Development.

He also expressed fear about whether the first treatments would be properly funded in this country.

“We need sensible partnerships here,” he said. “What we need to avoid is making a breakthrough such a drug that can destroy plaque but is then refused by the NHS. I do have fears about that,” he said.

The National Institute for Health and Clinical Excellence was taken to court a decade ago for limiting funding drugs which control symptoms of dementia.

Dr Gillings, the founder of a US company which runs clinical trials, said public rationing bodies needed to consider the long-term benefits of funding even modest advances in drug treatment which might ultimately lead to a cure.

The humane case for offering treatments which could improve quality of life, as well as the economic grounds, should be taken into account he said.

Early drugs were likely to be “a little expensive” given the years spent on research, but given the huge size of the market for drugs, treatment costs would fall, he speculated.

Handing over the post of chair of the council, Dr Gillings said the body, launched by David Cameron following the 2013 G8 summit, ensured that experts from across the world worked together in the search for a cure.

New chairman Dr Yves Joanette, scientific director at the Canadian Institutes of Health Research Institute of Aging, said: “The challenge is so huge here. We can get a man to the moon but we don’t know the brain works.

“We are probably facing a multiplicity of types of diseases that we call dementia. We need to be able to stratify that, to break it into different types.

“To do that you don’t just need the best brains across the world working together, you also need the big data that comes with that.”

Dr Margaret Chan, World Health Organisation Director-General, said: “There is a tidal wave of dementia coming our way worldwide. We need to see greater investments in research to develop a cure, but also to improve the quality of life of people living with dementia and the support given to their caregivers.”

Jeremy Hunt, Health Secretary said the council had made “remarkable progress” so far.

“While we are seeing progress in drug development and greater understanding of this disease, there can be no cause for complacency and I look to the World Dementia Council to use their expertise and global reach to drive governments, industry and regulators to further action,” he said.

Jeremy Hughes, chief executive of Alzheimer’s Society, said: “Dementia doesn’t stop at UK borders and is undoubtedly the biggest health and care challenge facing the world today. Efforts to improve the lives of people with dementia around the world have taken a leap forward in recent years, particularly on beating the stigma and finding new treatments. With the dementia crisis snowballing, strong global leadership is essential.”

To take part in UK dementia research: www.joindementiaresearch.nihr.ac.uk