The problem with developing treatments for dementia is that it requires an extraordinarily detailed understanding of our most complex organ - the brain.
And that has meant far more has been spent on research over the last than has been recouped by marketable therapies.
There have been clinical trials on 104 potential drugs in the last 15 years but just three have received regulatory approval. £29 billion has been spent on dementia R&D with very little to show for it.
No wonder that for every one scientist researching dementia in the UK, there are six working on cancer.
And no wonder David Cameron's Dementia Envoy, Dr Dennis Gillings, says the target to find a cure or an effective treatment by 2025 is "impossible" without better incentives for investment, and a loosening of the red tape surrounding clinical trials.
But for research to have any real chance of untangling what does cause the many forms of dementia, it has to be a global endeavour.
In particular the USA has to recognise funding research into dementia is important.
Yet in 2011 the US National Institutes of Health committed less than $500 million to dementia research, compared to more than $6 billion on cancer.
David Cameron is writing to Barack Obama and the other G8 leaders urging them to follow his lead. Their backing is badly needed.
The UK may get kudos from being a world leader in dementia research, but on our own progress will continue to be as "achingly slow" as the Dementia Envoy reports today.