Association Between bilingualism and Amyloid Uptake Among Mexican Americans: An HABS-HD Study

Background: Bilingualism is thought to provide protective benefits in regions of the brain associated with the onset of Alzheimer's Disease (AD). While there has been extensive research on bilingualism's effect on grey matter volume, there is no study to date that has examined the relationship between bilingualism and amyloid burden within brain regions characteristically impacted by AD. This study aims to fill this gap by comparing amyloid deposition in Mexican Americans who are either monolingual or bilingual. Methods: Data were analyzed on n=34 Hispanic, Mexican Americans (n=16 bilingual; n=18 monolingual) participants enrolled in a study of health disparities with available Amyloid PET scans. PET Amyloid scans were conducted using florbetaben (18F) on a Siemens Biograph Vision 450 whole-body PET/CT scanner. PET Amyloid SUVR levels were generated from the following Regions of Interest (ROIs): Frontal, Anterior Posterior Cingulate, Lateral Parietal, Lateral Temporal, and Global, with global SUVR>1.08 determined as the cut-off for Amyloid positivity. Independent t-test and chi-square tests were conducted to examine group differences in language status across demographic variables. One-way ANOVAs were conducted to examine groups differences in APOE e4 carrier status as well as in language capabilities (monolingual, bilingual) and PET amyloid SUVR. Follow-up analyses examining language capabilities were split by APOE e4 carrier status (carrier, non-carrier). Results: In comparison to APOE e4 non-carriers, APOE e4 carriers experienced significantly increased amyloid burden across all regional areas, including global (p< 0.05). Bilingual APOE e4 non-carriers showed a significantly increased amyloid deposition in the Anterior/Posterior Cingulate cortex in comparison to monolingual APOE e4 non-carriers. Furthermore, among APOE e4 non-carriers, there was a trend towards significance for global amyloid uptake (p=0.059), with bilinguals again showing higher amyloid burden. Among APOE e4 carriers, no significant associations were found between language status (monolingual, bilingual) and amyloid uptake. Discussion: This was the first study to examine the association between bilingualism and amyloid burden within specific cortical regions of the brain. Results contradicted previous work observing the role of the posterior/anterior cingulate in bilingualism. The trend towards significance in global amyloid uptake for APOE e4 non-carriers favored increased burden in bilinguals, a result opposite of what was expected. Bilingualism is complex and multifactorial and further work is greatly needed to understand the link it has with amyloid burden particularly by disease state.