“The rates of dementia differ greatly around the world, from the lowest rates in Africa, India, and South Asia, to the highest rates in Western Europe and especially North America. Is it all just genetics? Well, the incidence of dementia and Alzheimer’s disease is significantly lower for Africans in Nigeria than for African Americans in Indianapolis, for example—up to five times lower.”
He notes that:
“Alzheimer’s rates of Japanese-Americans living in the U.S. are closer to that of Americans than to Japanese. When people move from their homeland to the United States, Alzheimer’s rates can increase dramatically. Therefore, when Africans or Asians live in the United States and adopt a Western diet, their increase in Alzheimer’s risk suggests that it’s not genetics.”
But read the whole thing.
You can see a map of Alzheimer’s/dementia deaths by country here.