Dementia is a disease that mostly effects elderly patients, so make the denominator the number of people in the 65-100 age group.

Roughly 10% of the world population, or 800 million, fall within this age group.

57_000_000 / 800_000_000 ~= 7%

That's quite a large number of people who will be impacted.

> a number that is expected to almost triple to 152.8 million cases by 2050

I don't have the statistics for the elderly population in 2050, but if we assume the proportion is the same (it won't be), then the higher incidence case rate is sobering.

It's nearly 20%.