Longitudinal Effects of Bilingualism on Cognitive Resilience Across Clinical Syndromes in Alzheimer's Disease and Related Dementias (ADRD)

This longitudinal study examines the statistical modeling of bilingualism's role in enhancing cognitive resilience and its neuroprotective effects against Alzheimer's disease and related dementias (ADRD). We analyzed data from 453 participants (375 monolingual, 48 bilingual) clinically categorized into five groups: healthy controls and memory, language, behavioral, motor-predominant syndromes over a 10-year follow-up period. To address challenges associated with unbalanced data common in longitudinal clinical trials, we implemented a dual statistical approach: robust non-parametric methods (including Aligned Rank Transform ANOVA) for cross-sectional comparisons, and linear mixed-effects modeling with appropriate covariance structures to analyze repeated measures over time. Our longitudinal analyses revealed that bilingual speakers experienced significantly slower functional decline in specific domains, particularly language-related assessments, compared to monolingual speakers. These domain-specific protective effects were most pronounced in participants with predominant language syndromes, including non-fluent/agrammatic (N = 21), semantic (N = 18), and logopenic variant (N = 20) primary progressive aphasia. These findings underscore how bilingualism may serve as a protective factor against cognitive decline by enhancing resilience and slowing functional deterioration in Alzheimer's disease and related dementias (ADRD). Additionally, they highlight the importance of advanced statistical modeling in addressing challenges such as unbalanced data and distinguishing biological variability from technical noise in a clinical research scenario.

Bilingualism

Neurodegeneration

Random Forest

Longitudinal analysis

ADRD

Mixed-effects modeling 

Statistical Data Science

Symposium on Data Science and Statistics (SDSS) 2025