Dementia will affect more than 150m people worldwide by 2050

Today an estimated 57m people live with dementia, an incurable degenerative condition that, in its worst phases, leaves them dependent on 24-hour care. A new study published in Lancet Public Health adds weight to predictions that that number is going to explode. Its projection, that the number will treble to 152.8m by 2050, with women disproportionately affected by the condition, is in line with forecasts made for the past seven years or more. But unlike earlier studies, which relied on global projections, this one took into account country-level estimates and specific risk factors.

It still faced serious limitations in the quality of data from individual countries, which use different methodologies and often even different definitions of dementia. That the conclusion is so similar to that of earlier studies underlines that the most important risk factor remains a simple one: age. Dementia is a condition that accompanies dozens of different diseases—of which much the most important is Alzheimer’s, accounting for 60-80% of cases—to almost all of which people become more susceptible as they get older. Most of the projected increase in dementia is the result of two global factors: increases in population and longevity.

That is why the biggest increases are in parts of the world with the fastest-growing populations, such as sub-Saharan Africa. This means that dementia will no longer be, as at present, predominantly a rich-world problem. In rich countries, meanwhile, increases in dementia are predicted largely because populations are getting older.

The Lancet Public Health study also takes into account risks that, unlike age, are modifiable: smoking, obesity, high blood-sugar and low education. Already, in North America and Europe, the incidence of dementia—that is, the percentage of people of any given age with the condition—has fallen noticeably, perhaps because of better access to and quality of education and improved cardiovascular health. The study finds that globally, these advances will reduce the number of people expected to have dementia by 6.2m. However, increases in obesity, smoking and high blood pressure in some countries will more than offset that, leading to an additional 6.8m cases.

All these projections are of course imprecise. But the argument of this study and many before it is indisputable: that the world will have to learn to live with huge numbers of people with dementia. There is, as yet, no vaccine and no cure, although America last year approved a drug for the treatment of early-stage Alzheimer’s. No country has yet worked out how it is going to pay for the care these people will need. And in many places it is far from clear where the carers will be found. ■

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