Of all the troubles facing the world, the rising prevalence of dementia might seem among the less pressing. The reason behind it — longer life spans — is to be cheered; it does not advance at the speed of a viral infection but with the ponderous inevitability of demographic change; and its full effects will not be felt until far into the future.

But dementia is already a global emergency. Even now, more people live with it than can be looked after humanely. No cure is in the offing. And no society has devised a sustainable way to provide and pay for the care that people with it will need.

"Dementia" is an umbrella term for a range of conditions, with a variety of causes, of which the most common is Alzheimer's disease, accounting for 60-80% of cases. It usually starts with forgetfulness and a mild loss of cognitive functioning. But as it advances, people lose the ability to look after themselves. Many require round-the-clock care long before they die.

By some estimates, 1.7% of 65- to 69-year-olds have dementia and the risk of developing it doubles every five years after that. At present, about 50 million people around the world have the condition, a number expected to rise to 150 million by 2050.

The problems these numbers will bring everywhere have already been felt in countries where people are older, and especially acutely during lockdowns — witness the difficulty of looking after people with dementia in their own homes, and the large numbers in overstretched care homes who receive little individual attention. As families shrink, single children and grandchildren will struggle to cope with their old folk. Already, dementia care has had a knock-on effect on general health care. Before the pandemic as many as a quarter of beds in British hospitals were occupied by people with dementia. There was nowhere else for them to go.

Governments should act now to lessen the social and economic harm from the growing prevalence of dementia. The first step is to recall the urgency with which many were promising to tackle the problem just a few years ago. Instead, funding for research work on dementia has lagged far behind that for cancer or coronary heart disease. And as the pandemic hampers or prevents clinical trials and research, and sucks resources away from other areas, dementia risks again being left behind.

Governments also need to think about long-term care for people with dementia. The question that is most often asked is how to pay for it. Japan's compulsory long-term-care insurance scheme, requiring everyone aged 40-65 to pay a premium, seems attractive, as it avoids penalizing the young. But it is not self-financing. The increasing burden there as elsewhere will fall on individuals and the taxpayer.

And an even more fundamental question than who pays for care is: who will do it? Undertaken with humanity and dignity, it is extremely labor-intensive. Technology can help lighten the load — using remote monitoring to let people stay at home and, perhaps in future, robots to perform some basic tasks. But looking after people with dementia requires people.

The job is usually classified as low-skilled and is often poorly paid. In fact it demands huge reserves of patience, empathy and kindness. It should be better rewarded and more highly regarded even though that would add to the bill.

Lastly, evidence suggests that as many at 40% of cases of dementia can be delayed or averted by changing behavior earlier in life. The trouble is that public-health campaigns have a patchy record and they do nothing for dementia's most intractable pre-existing condition — old age.

No cure, insufficient financing and a tricky public-health message: perhaps that is enough to make you throw up your hands in despair. Instead, however, it only underlines how the solutions to dementia, like the disease itself, will take decades to unfold. It is yet another reason to start working on them right away.

Copyright 2020 The Economist Newspaper Limited, London. All Rights Reserved. Reprinted with permission.