A cure for dementia could be found within five years, the leader of the global council on the disease has said.
Dr Dennis Gillings, outgoing chairman of the World Dementia Council, said recent scientific progress had surpassed his expectations, with two potential breakthroughs now on the horizon.
In an interview with The Daily Telegraph, he said he was "optimistic" that treatments that could remove the plaques in the brain linked with dementia, and those to unscramble the neural tangles that characterise the disease, might be developed as soon as 2020.
Dr Gillings, appointed by David Cameron in 2013 to create the global council, 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 that scientists increasingly believed it had been a mistake to treat dementia as one disease, saying it was likely that breakthroughs would come from targeting subtypes of the condition. "We used to just think cancer; now we know there are many different types, with different treatments. We need to approach dementia similarly," he said.
Current medications mask symptoms but do not delay the onset of disease. Dr Gillings, the founder of a US company that runs clinical trials, said progress was being made on treatments that might halt or reverse the progress of dementia, with some kind of brain training used to help rebuild lost neural pathways.
Other treatments could "untangle some of the neural tangles" to enable regeneration, he said.
Saluting recent British investment in science, and the creation of a 150 million Dementia Research Institute, he said that, none the less, breakthroughs were more likely in the US, which put more money into research.
"We need sensible partnerships here. What we need to avoid is making a breakthrough on such a drug that can destroy plaque but is then refused by the NHS," he said.
Jeremy Hughes, chief executive of the Alzheimer's Society, said: "Dementia doesn't stop at UK borders, and is undoubtedly the biggest health and care challenge facing the world."With the dementia crisis snowballing, strong global leadership is essential."