The impact of bilingualism on cognitive reserve/resilience using socio-demographically and linguistically diverse populations

PROJECT SUMMARY Alzheimer’s disease (AD) is the most common form of dementia, impacting millions of people globally. Despite the advancements in understanding fundamental biological constructs of AD and the fact that the global population of bilinguals has outnumbered monolinguals, our understanding of the impact of bilingualism on AD/ADRD (AD and related dementias) remains limited. Previous bilingualism studies suggest that the bilingual experience impacts cognition and AD/ADRD, albeit in varying scale that stems from variabilities in demographic profiles and prevalence of ADRD risk factors. The overarching goal of this study is to directly interrogate the neural and sociocultural aspects of bilingualism across multiple race/ethnic groups, with specific emphasis on deconstructing the links between bilingualism and AD. To accomplish this, the University of California, San Francisco Alzheimer's Disease Research Center in California, the National Institute of Mental Health and Neurosciences in India, and the Health and Aging Brain Study- Health Disparities study in Texas will jointly assemble one of the largest, multicultural, multilingual, and well-characterized cohort of 2,200 individuals representing the world’s most commonly spoken languages: Chinese, Spanish, Kannada, and English languages. This study team will collect cross-sectional data on cognition, imaging, molecular biomarkers, language background, and SDOH, and follow-up language, SDOH, and cognitive data for three years. We intend to build a theoretical framework on the cognitive role of bilingualism by deconstructing bilingualism and examining its features via a multidimensional lens. We will examine the inter-relationship of this multidimensional bilingualism construct with cognition and social determinants of health using structural and functional magnetic resonance imaging and AD/ADRD molecular biomarkers. Our central hypothesis is that specific bilingualism features would influence the cognitive trajectory by improving executive control through the mechanism of brain and cognitive reserve even after accounting for social determinants of health and AD/ADRD biomarkers. This proposed study will provide novel mechanistic insights into the multidimensionality of bilingualism and create an exclusive opportunity to study the cognitive relevance of bilingualism using socio-demographically and linguistically diverse cohorts. This study also has the unique settings to evaluate the generalizability of the proposed cognitive-bilingualism theoretical framework across populations that differ in sociocultural, demographic, and linguistic background.