It has long been known that bilingualism has cognitive benefits for older adults. Research shows it can delay the onset of Alzheimer’s disease by up to five years compared to monolingual adults. This is one of many lifestyle factors that can contribute to the brain’s resilience as we age.
This is evident from a new study published in the journal Bilingualism: language and cognitionConcordia researchers use neuroimaging methods to investigate brain resilience in brain areas linked to language and aging.
They found that the hippocampus in bilinguals with Alzheimer’s disease was noticeably larger than in those who were monolingual, when they were matched for age, education, cognitive function and memory.
“There was more brain mass in the hippocampus, the most important area in the brain for learning and memory and which is strongly affected by Alzheimer’s disease,” said the study’s lead author, PhD student Kristina Coulter. She coauthored the study with Natalie Phillips, a professor in the Department of Psychology and the Concordia University Research Chair (Tier 1) in Sensory-Cognitive Health in Aging and Dementia.
The researchers compared the brain characteristics of monolingual and bilingual older adults who were cognitively normal, who were at risk for subjective cognitive decline or mild cognitive impairment, or who had been diagnosed with Alzheimer’s.
They found that although there was evidence of hippocampal atrophy among individuals with mild cognitive impairment and Alzheimer’s disease who were monolingual, there was no change in hippocampal volume in bilinguals across the continuum of Alzheimer’s development.
“The brain volume in the Alzheimer’s-related region was the same in the healthy older adults, the two risk states and the Alzheimer’s disease group in the bilingual participants,” says Coulter. “This suggests that there may be some form of brain maintenance related to bilingualism.”
Localized resilience
Brain maintenance, brain reserve and cognitive reserve are the three components of brain resilience, a concept that refers to the brain’s ability to cope with changes associated with aging.
Brain maintenance is the continued ability to maintain its form and function as it ages. It is believed that mental stimulation such as bilingualism, along with a healthy diet, regular exercise, good sleep and good sensory health, help protect the brain from deterioration.
Brain reserve refers to the size and structure of the brain. Brains with greater reserves can maintain normal functions due to the extra volume or capacity of brain material, even if they experience damage or atrophy due to aging, including from pathological diseases such as Alzheimer’s disease.
Cognitive reserve refers to the way a brain can use alternative pathways to maintain functionality even when it is damaged or experiences shrinkage due to aging. Brains with greater cognitive reserve can use areas of the brain other than those usually associated with a particular function, such as language or memory, thanks to a lifetime of accumulated cognitive flexibility.
Coulter notes that they did not find bilingualism-associated brain reserve in the language-related brain areas, or cognitive reserve in the Alzheimer’s-related brain areas.
Speaking more than one language is one of many ways to be cognitively and socially engaged, which promotes brain health. “This study was unique in that it was able to look at the potential impact of being bilingual on brain structure across the spectrum of dementia risk, ranging from individuals who were cognitively normal, to those at higher risk of developing the Alzheimer’s disease, to those who actually have the disease.”
Natalie Phillips, Professor in the Department of Psychology and the Concordia University Research Chair (Tier 1) in Sensory-Cognitive Health in Aging and Dementia
Future work from these Concordia researchers will delve into whether multilingualism has a similarly positive impact on brain networks.
For this study, the researchers used data from the Comprehensive Assessment of Neurodegeneration and Dementia Study (COMPASS-ND) and the Consortium for the Early Identification of Alzheimer’s disease-Quebec (CIMA-Q).
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Magazine reference:
Coulter, K., & Phillips, N. A. (2024). Bilinguals show evidence of brain maintenance in Alzheimer’s disease. Bilingualism Language and cognition. doi.org/10.1017/s1366728924000221.