Speaking two languages may keep the mind sharp longer than knowing only a single language, even in those who can't read.
Scientists reviewed the records of 391 bilingual and 257 monolingual patients diagnosed with dementia between 2006 and 2012 at a clinic in Hyderabad, India. Patients who spoke two languages developed the first signs of dementia an average of 4.5 years later than people who only spoke one language.
Additional results suggest that education alone cannot account for the difference. Bilingual speakers who could not read developed dementia an average of 6 years later than single-language speakers, the researchers report November 6 in Neurology.
Knowing three or more languages did not provide any extra benefit, the authors note.