It has replaced cancer as the disease people fear most. As doctors get better and better at treating, and in some cases curing, cancer, the prospect of a slow descent into dementia frightens people more than almost any other fate.
And it's a prospect that faces more and more people. That's why the G8 nations are meeting in summit on Wednesday to look at new ideas for research into dementia.
They say "follow the money" to find the story so let's look at some figures. First a broad observation: we spend about 100 times more on cancer research than we do on research into dementia. That seems simply a distortion. But will more money solve the problem? It's estimated drug companies and governments have spent $40 billion trying to develop treatments for dementia. But successes have been few and far between.
One reason is that human trials of candidate drugs are very expensive. Thousands of patients have to be given the drug to test it's safe and effective. And about half the people in trials get a placebo for comparison so get no benefit.
So here's a new idea from IMI - a consortium of drug companies, the European Commission, doctors and patients with a €2 billion budget. They will be funding new kinds of trials. More than one drug at a time will be put into the trial, so fewer patients are on placebos. Drugs that seem to be working can be given to more people. Drugs that don't seem to be working can be withdrawn. All good ideas.
But some experts think we are missing a trick - we're not spending enough on preventing dementia. In the UK, research councils spent £140 million on dementia since 2006 - but only 0.1 per cent was on prevention. Over 100 experts have signed a letter to the G8 calling for more preventative research.
And we know prevention works. About half the burden of dementia could be reduced by encouraging the Big Five:
taking moderate exercise
keeping your body weight low
drinking in moderation
The results of the latest research are dramatic. Scientists from Cardiff University monitored the health of over 2,000 men over 35 years. That's an incredibly long time. The researchers say if their men had followed four of the Big Five rules, there would have been 60 per cent fewer of them with dementia.
Clearly science and medicine need to attack dementia on every front. Otherwise what is now a threat that strikes fear into people's' hearts, could become an epidemic and a burden that threatens the very fabric of societies.