Evidence for bilingualism as a cognitive reserve factor in biomarker-confirmed Alzheimer's disease.

INTRODUCTION

Bilingualism is a proposed cognitive reserve factor that delays symptom onset in Alzheimer's disease (AD), though current evidence lacks biomarker confirmation. This retrospective study examined bilingualism's association with symptom onset across AD clinical stages, including biomarker-confirmed cases.

METHODS

Participants from the Sant Pau Memory Unit spanning amnestic mild cognitive impairment (MCI), amnestic dementia, and biomarker-confirmed AD were analyzed, with balanced representation of active and passive Spanish-Catalan bilinguals. Linear regression models evaluated associations between bilingualism and reported age at symptom onset, controlling for education, sex, and disease severity.

RESULTS

Active bilingualism was associated with delayed symptom onset in amnestic MCI (2.21 years), amnestic dementia (1.42 years), and biomarker-confirmed AD (1.45 years; ps < .05). Higher education was associated with earlier onset, likely representing healthcare seeking behavior.

DISCUSSION: Bilingualism protects against earlier symptom manifestation in MCI and AD, supporting bilingualism as a contributor to cognitive reserve.