Monolinguals outperform bilinguals in language but not executive function in aging and cognitive impairment

People with subjective cognitive decline (SCD) self-report declining cognitive function, although objective cognitive performance remains normal. SCD is a risk factor for mild cognitive impairment (MCI) and dementia. Previous research has found differences in cognitive performance in bilinguals compared with monolinguals. We examined cognitive performance in older adults with and without SCD, and the association between bilingualism and cognitive performance in cognitively healthy older adults, people with SCD, and people with MCI, and the influence of bilingualism on the age of MCI diagnosis.

Adults aged 65+ (n = 264) rated their ability in French and English and self-perceived change in concentration and attention, memory, and word-finding. They then completed neuropsychological tests assessing language, memory, and executive function. Participants were monolingual or bilingual and were older adults, reported amnestic or nonamnestic SCD, or had MCI.

No differences in cognitive performance were observed between older adults and people with SCD, while people with MCI had lower performance on nearly all tasks. Monolinguals outperformed bilinguals in the Boston Naming Test, letter-number sequencing, California Verbal Learning Test, FAS, animal, vegetable/musical instrument, and A/F switch fluency tasks, but group performance did not differ on executive function tasks. Sensitivity analyses using English L1 bilinguals who completed the first administration of the language tasks in the English or bilingual version showed that monolinguals outperformed bilinguals on only the Boston Naming Test. Monolinguals had a later age of MCI diagnosis than bilinguals in our sample.

These findings suggest that the protective effect of bilingualism reported elsewhere in the literature is not universal. (PsycInfo Database Record (c) 2025 APA, all rights reserved).