The Contribution of Bilingualism to Cognitive Functioning and Biological Markers in the Progression of Normal and Abnormal Aging

Controversy surrounds the idea that bilingualism leads to enhanced executive function (EF) and brain volume changes, potentially leading to delays in cognitive decline and dementia onset. The purpose of this research was to explore these claims in a sample of elderly monolinguals and bilinguals. This study explored gray matter volume (GMV) in 214 monolinguals and bilinguals (Mage = 71.21, SD = 7.53) who were cognitively normal (CN) or diagnosed with Mild Cognitive Impairment (MCI) or dementia. Neuropsychological performance was also examined between CN and MCI monolinguals and bilinguals (N = 153) across two visits. Scores from the Digit Span Backwards, Stroop interference, Trail Making Test A minus Trail Making Test B, and category fluency average scores were used. Magnetic Resonance Imaging (MRI) brain regions associated with memory, language, and EF were selected. Additionally, the study examined how a Bilingualism Index (BI) and the age of acquisition of English could predict GMV and EF in Spanish/English bilinguals whose native language was Spanish.
Lastly, the initial age of cognitive decline across language groups was compared. Results suggested higher GMV in language and EF regions in bilinguals, but differences were not found in memory regions. Furthermore, neuropsychological performance over time did not vary across language groups; however, bilinguals exhibited reduced Stroop interference as well as lower scores on Digit Span Backwards and category fluency. The age of acquisition of English did not predict GMV or EF scores, while the BI predicted category fluency, with lower scores associated with a higher degree of balanced bilingualism. Overall, the influence of bilingualism appears to be reflected in increased GMV in specific language and EF regions relative to neuropsychological performance.