Bilingualism has long been known to have cognitive benefits for older adults. Research shows it helping delay the onset of Alzheimer's disease by up to five years compared to monolingual adults.
Lindenberger, Ulman Li, Shu-Chen and Bäckman, Lars 2006. Delineating brain–behavior mappings across the lifespan: Substantive and methodological advances in developmental neuroscience. Neuroscience & ...