Naming performance in bilinguals with Alzheimer's disease and mild cognitive impairment

BackgroundThere is consistent evidence of a disadvantage in bilinguals' speech production compared to monolinguals in healthy individuals, but studies investigating this phenomenon in clinical populations such as mild cognitive impairment (MCI) and Alzheimer's disease (AD) are scarce. Given that both clinical groups are characterized by word-finding difficulties, understanding how bilingualism influences speech production in these populations is essential.ObjectiveTo investigate the effect of bilingualism on dominant-language speech production in individuals with MCI and AD relative to cognitively unimpaired (CU) older adults.MethodsEarly and highly proficient Catalan-Spanish bilinguals (active bilinguals) were compared to Spanish-dominant speakers with low proficiency in Catalan (passive bilinguals) using a picture-naming task. The study included 58 CU older adults, 66 patients with AD, and 124 individuals with MCI. Reaction times, accuracy, and error types were collected in the naming task in each individual's dominant language.ResultsFirst, we observed an advantage for active bilinguals compared to passive bilinguals, as indexed by faster responses, particularly for cognate words. Second, active bilinguals with MCI exhibited a disadvantage, making more naming errors than passive bilinguals with MCI, especially for non-cognates, including a higher incidence of cross-language intrusions and anomia. Third, passive bilinguals with MCI and AD showed more semantic errors than active bilinguals.ConclusionsDisadvantages in naming are discussed in terms of predictions from cognitive and linguistic theories, whereas potential advantages of speaking a second language are considered as a protective factor, consistent with frameworks such as cognitive reserve.