Does multilingualism affect the incidence of Alzheimer's disease?: A worldwide analysis by country.

It has been suggested that the cognitive requirements associated with bi- and multilingual processing provide a form of mental exercise that, through increases in cognitive reserve and brain fitness, may delay the symptoms of cognitive failure associated with Alzheimer's disease and other forms of dementia. We collected data on a country-by-country basis that might shed light on this suggestion. Using the best available evidence we could find, the somewhat mixed results we obtained provide tentative support for the protective benefits of multilingualism against cognitive decline. But more importantly, this study exposes a critical issue, which is the need for more comprehensive and more appropriate data on the subject.