Slide Slam L6
The influence of bilingualism on gray matter volume in the course of aging
Katharina Hild1,2, Johanna Stumme1,3, Christiane Jockwitz1,3, Svenja Caspers1,3, Stefan Heim1,2; 1Institute of Neuroscience and Medicine (INM-1), Research Centre Jülich, Jülich, Germany, 2Department of Psychiatry, Psychotherapy and Psychosomatics, Medical Faculty, RWTH Aachen University, Aachen, Germany, 3Institute for Anatomy I, Medical Faculty & University Hospital Düsseldorf, Heinrich Heine University, Düsseldorf, Germany
Aging is associated with variable cognitive and cerebral decline . Bilingualism seems to maintain cognitive functioning with aging . A structural correlate of this cognitive advantage during aging is termed brain reserve . Bilingualism was associated with higher gray matter volume (GMV) as a form of brain reserve in the inferior frontal gyrus (IFG) and inferior parietal lobule (IPL) [1, 4]. Interestingly, a cross-sectional study reported a steeper GMV decline for bilinguals , which remains to be confirmed longitudinally. Therefore, we investigated trajectories of mono- and bilingual’s GMV decline in a large-scale longitudinal study. We included 200 adults (19-79 years, 114 men, 87 monolinguals) from the population-based 1000BRAINS study . The sample was split into younger/older participants (median split: 62.8 years) and monolinguals/bilinguals (assessment: Language Experience and Proficiency Questionnaire ). For each participant, T1-weighted MR images were acquired (3T Siemens Tim-TRIO) at two time points (T1/ T2, mean interval 3.6 years). GMV was extracted from four regions of interest (ROIs) (Julich Brain atlas: left/right IFG  and left/right IPL ) using FreeSurfer’s longitudinal stream . For each ROI, mixed Analyses of Covariance (ANCOVAs) were conducted (covariates: sex/education/time interval) to assess (i) GMV changes over time, (ii) GMV differences for language groups (monolinguals/bilinguals) and age groups (younger/older participants) and (iii) the interaction between time point and language group. Results were significant at p < .05. There was higher GMV in bilinguals compared to monolinguals in the IPL (left: p=.023; right: p=.021), but not IFG. For all ROIs, GMV was higher in the younger group. While the left and right IFG and the right IPL displayed a similar GMV change in bilinguals and monolinguals (IFG left: p=.852, IFG right: p=.391; IPL right: p=.332), GMV decline within the left IPL was significantly steeper in bilinguals (p=.031). With higher GMV in bilinguals in IPL, but not IFG, bilingualism might contribute to brain reserve especially posteriorly . Higher GMV in the IPL in bilinguals might further reflect more pronounced activation of posterior brain regions during cognitive processing in bilinguals, underpinning the bilingual anterior-to-posterior and subcortical shift model . Importantly, bilinguals show a steeper GMV decline over time in the left IPL, indicating the bilingual’s brain reserve to diminish with aging. Contrastingly, mono- and bilinguals’ right IPL showed similar GMV changes over time, potentially highlighting a more persistent brain reserve here. Altogether, the current results could not only confirm cross-sectional observations  of a steeper GMV decline in bilinguals for the left IPL, but also indicate the necessity to additionally focus on hemispheric differences regarding age-related GMV changes in mono- and bilinguals. 1.Heim, S. et al., Neurobiology Aging, 2019. 2.Bialystok, E., Trends Cognitive Sciences, 2021. 3.Bartres-Faz D., Arenaza-Urquijo E.M., Brain Topography, 2011. 4.Abutalebi, J. et al., Journal Neurolinguistics, 2015. 5.Caspers, S. et al. Frontiers Aging Neuroscience, 2014. 6.Marian, V. et al., Journal Speech Language Hearing Research, 2007. 7.Amunts, K. et al., Journal Comparative Neurology, 1999. 8.Caspers, S. et al., NeuroImage, 2006. 9.Reuter, M. et al., NeuroImage, 2012. 10.Grundy, J.G. et al., Annals NY Acadamy Sciences, 2017.