Dementia is present in countries around the world. The prevalence and age of onset, may differ between regions.
As an example, in my home country the Netherlands: 256.000 people (on a population of 17M) has dementia. Because of the double aging of the population (more people grow older on average) this number is projected to increase exponentially. In 2050 more than 500.00o people will have dementia. (source: Alzheimer Nederland)
The American Alzheimer’s Association has made this movie about Alzheimer: