In the largest study on the topic to date, research shows that speaking a second language may delay the onset of three types of dementias. The research is published in the November 6, 2013, online issue of Neurology®, the medical journal of the American Academy of Neurology.
The study found that people who spoke two languages developed dementia four and a half years later than people who only spoke one language.
"Our study is the first to report an advantage of speaking two languages in people who are unable to read, suggesting that a person's level of education is not a sufficient explanation for this difference," said study author Suvarna Alladi, DM, with Nizam's Institute of Medical Sciences in Hyderabad, India. "Speaking more than one language is thought to lead to better development of the areas of the brain that handle executive functions and attention tasks, which may help protect from the onset of dementia."
For the study, 648 people from India with an average age of 66 who were diagnosed with dementia were evaluated. Of those, 391 spoke two or more languages. A total of 240 had Alzheimer's disease, 189 had vascular dementia and 116 had frontotemporal dementia, with the remainder having dementia with Lewy bodies and mixed dementia. Fourteen percent were illiterate.
People who spoke two languages had a later onset of Alzheimer's disease, frontotemporal dementia and vascular dementia than people who spoke only one language. The difference was also found in those who could not read. There was no additional benefit in speaking more than two languages.
The two-language effect on age of dementia onset was shown separately of other factors such as education, gender, occupation and whether participants lived in the city or country.
"These results offer strong evidence for the protective effect of bilingualism against dementia in a population very different from those studied so far in terms of its ethnicity, culture and patterns of language use," Alladi said.
American Academy of Neurology