Bilingualism in adult population without cognitive impairment: its relationship with aging in structural neuroimaging. A cross‐sectional study.

Abstract

AbstractBackgroundAging is consistently associated with cortical gray matter (GM) reductions. Bilingualism has been described as a potential reserve contributor for successful brain aging and has been associated with a variety of structural changes in cortical morphology. In this study we aim to: 1) Explore differences between bilinguals and monolinguals on the whole brain cortical thickness, area and volume, 2) explore if correlations between age and cortical measures are different between bilinguals and monolinguals, and 3) to evaluate age‐bilingualism interaction effects on the cortical characteristics.MethodCross‐sectional study with healthy volunteers from the Gipuzkoa Alzheimer Project (GAP) cohort. Cognitively unimpaired (CDR Global Score = 0) with available 3T MRI were included and classified as bilinguals or monolinguals based on daily use of both Spanish and Basque languages or only Spanish. Subjects with diffuse white matter lesions (Fazekas scale = 3) were excluded. Cortical reconstruction was performed with Freesurfer package v5.1. as described in Montal et al., 2017. Analyses were conducted in the whole brain using linear modeling of the maps and Monte Carlo simulation corrected for multiple comparisons as implemented in FreeSurfer’s QDEC interface.ResultSample included 88 bilinguals and 83 monolinguals (see Table 1 for demographic and clinical characteristics). Whole brain cortical thickness, area or volume were not significantly different between groups. Age‐cortical thickness and volume correlation maps showed broader areas of negative associations in the monolingual than in the bilingual group, and inverse associations in the relationship with area characterized by negative correlations in monolinguals and positive and negative correlations in bilinguals (Figure 1). More specifically, significant age‐bilingualism interactions were found for thickness in the right superiorfrontal gyrus (p = 0.012), and for the surface area, in the inferiorparietal (p = 0.0001), supramarginal (p = 0.043) and lingual (p = 0.042) regions of the left hemisphere.ConclusionCortical thickness and area variations occurring in relation to aging in cognitively healthy individuals could be modulated by bilingualism.