An article in The Telegraph (U.K.) touts University of Edinburgh research findings that learning a second language can somehow slow brain aging and postpone dementia, even if the language is learned in adulthood. A natural experiment is suggested.
Most Americans are monolingual whereas many Europeans are multilingual. If the above is accurate, the prevalence of dementia at any given age should be lower in Europe than in the U.S. My question: Is it the case?
I suspect contaminating variables in the U.K. study. In the U.K. knowing a second language may be a proxy variable for social class, unless large numbers of immigrants were included in the sample. Children who attend private boarding schools are more likely to be taught a second or third language than youngsters who attend neighborhood schools run by the government. Plus their parents are more likely to vacation abroad in places where knowing French or Spanish is useful.
Another possible contaminant: suppose most of the multilingual subjects were immigrants who eat substantially different diets than ethnic Brits, Scots, and Welsh. Diet can certainly affect brain health.
