Bilingualism is associated with a later age of symptom onset in bilinguals with Alzheimer’s disease positive biomarkers

Abstract

AbstractBackgroundCognitive reserve factors may provide protection against the manifestation of symptoms associated with neurodegenerative diseases (Stern, 2012). Although results are mixed, it has been observed that bilingualism may contribute to cognitive reserve by delaying the age of onset of symptoms of Alzheimer’s disease (AD) (e.g., Alladi et al., 2013, 2017; Bialystok et al., 2007, 2010; de Leon et al., 2020).MethodsIn the current study, we examined the effects of bilingualism on age of symptom onset in a large cohort of Catalan‐Spanish bilingual speakers (n = 446) with positive Alzheimer’s disease cerebrospinal fluid biomarkers. We conducted a retrospective study in which participants were characterized as bilingual or monolingual based on self‐report at the time of neuropsychological testing. Analyses of covariance (ANCOVA) were conducted to investigate the association between bilingualism and age of symptom onset while controlling for a proxy of disease severity (Mini‐Mental State Exam (Folstein et al., 1975) and education.ResultsThe results of our ANCOVA revealed that Catalan‐Spanish bilinguals with AD positive CSF biomarkers present with a significant, approximate two‐year delay in symptom onset relative to monolingual speakers (see Figure 1; bilingual M = 71.41, monolingual M = 69.75).ConclusionAlthough previous reports in the literature indicate that bilingualism may delay the onset of symptoms on the order of 4‐5 years, we observed an approximate 2‐year difference in the onset of symptoms. This finding is consistent with previous literature conducted in Catalan‐Spanish bilinguals (Calabria et al., 2020) and likely reflects that even ‘monolingual’ speakers in this particular sociocultural context are exposed to more than one language and may exhibit a form of passive bilingualism.