The effect of bilingualism on amnestic mild cognitive impairment.

OBJECTIVES Previous reports have found that lifelong bilingualism is associated with a delay in the onset of dementia, including Dementia of the Alzheimer's Type (DAT). Because amnestic mild cognitive impairment (aMCI) is often a transition stage between normal aging and DAT, our aim in this paper was to establish whether this delay in symptom onset for bilinguals would also be seen in the onset of symptoms of aMCI and whether this delay would be consistent in different subtypes of aMCI. METHOD We examined the effect of bilingualism on the age of diagnosis in individuals with single- or multiple-domain aMCI who were administered a battery of neuropsychological tests and questionnaires about their language and social background. RESULTS Our results showed an interaction between aMCI type and language history. Only individuals diagnosed with single-domain aMCI demonstrated a later age of diagnosis for bilinguals (M = 79.4 years) than monolinguals (M = 74.9 years). DISCUSSION This preliminary evidence suggests that the early protective advantage of bilingualism may be specific to single-domain aMCI, which is the type of aMCI most specifically associated with progression to DAT.