The Contributions of Active Spanish-English Bilingualism to Cognitive Reserve among Older Hispanic Adults Living in California

Objective Bilinguals may be able to retain similar levels of cognitive functioning given age and/or Alzheimer’s Disease-related neurodegeneration, compared to monolinguals. Many studies have yielded equivocal findings that may be explained by within-group differences among bilinguals, such as frequency of language use. The current study aimed to clarify the role of frequency of bilingual language use (i.e., active versus passive) in the association of brain structure and memory. We hypothesized that active bilinguals would demonstrate better memory performance compared to passive bilinguals and monolinguals, and that active bilingualism would buffer the effects of temporal lobe integrity on memory. Participants and Method In a longitudinal aging study, 217 older Hispanic adults (Age M = 74 years, SD = 6; 70% women) underwent neuropsychological evaluation and 1.5T MR imaging. Bilingualism was determined by self-reported use of English and Spanish. Active bilinguals reported using both languages daily. Multiple regression tested main effects and interactions of bilingualism and entorhinal cortical thickness on semantic and episodic memory, adjusted for age, sex/gender, and education. Results Bilingualism was associated with better semantic memory(F[2,209] = 6.25, p = .002) but not with episodic memory(F[2,209)] = 0.34, p = .71). There was a significant bilingualism X entorhinal cortical thickness interaction on semantic memory (β = -.26, p = .02), indicating that active bilinguals were better able to maintain cognitive functioning with lower cortical thickness, compared to passive bilinguals and monolinguals. Conclusions Active bilingualism may protect semantic memory against cortical thinning of the entorhinal cortex. Future studies will explore whether this relationship remains after accounting for additional environmental and sociocultural factors (e.g., immigrant status) that influence the ability or opportunity to become bilingual, and whether active bilingualism affects cognitive trajectory in late life.