Bilingualism’s effect in mild cognitive impairment and Alzheimer’s

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A Concordia University study focusing specifically on the effects of knowing a second language for patients with Alzheimer’s disease and mild cognitive impairment, found bilingualism may also delay the cognitive effects of disease-related atrophy.

After more than a decade of research, this much we know: it’s good for your brain to know another language. A new Concordia University study goes further, however, focusing specifically on the effects of knowing a second language for patients with Alzheimer’s disease (AD) and mild cognitive impairment (MCI; a risk state for AD).

“Most of the previous research on brain structure was conducted with healthy younger or older adults,” says Natalie Phillips, a professor in the department of psychology. “Our new study contributes to the hypothesis that having two languages exercises specific brain regions and can increase cortical thickness and grey matter density. And it extends these findings by demonstrating that these structural differences can be seen in the brains of multilingual AD and MCI patients.”

Phillips and her team are the first to use high-resolution, whole-brain MRI data and sophisticated analysis techniques to measure cortical thickness and tissue density within specific brain areas. Namely, they investigated language and cognition control areas in the frontal regions of the brain, and medial temporal lobe structures that are important for memory and are brain areas known to atrophy in MCI and AD patients.

“Previous studies used CT scans, which are a much less sensitive measure,” says Phillips, founding director of Concordia’s Cognition, Ageing and Psychophysiology (CAP) Laboratory.

The study looked at MRIs from participating patients from the Jewish General Hospital Memory Clinic in Montreal. Their sample included 34 monolingual MCI patients, 34 multilingual MCI patients, 13 monolingual AD patients and 13 multilingual AD patients.

Phillips believes their study is the first to assess the structure of MCI and AD patients’ language and cognition control regions. It is also the first to demonstrate an association between those regions of the brain and memory function in these groups, and the first to control for immigration status in these groups.

“Our results contribute to research that indicates that speaking more than one language is one of a number of lifestyle factors that contributes to cognitive reserve,” Phillips says. “They support the notion that multilingualism and its associated cognitive and socio-cultural benefits are associated with brain plasticity.”

Phillips and her team are already building on their findings. “Our study seems to suggest that multilingual people are able to compensate for AD-related tissue loss by accessing alternative networks or other brain regions for memory processing. We’re actively investigating that hypothesis now.”

Two independent lines of research provide evidence that speaking more than one language may 1) contribute to increased grey matter in healthy younger and older adults and 2) delay cognitive symptoms in mild cognitive impairment (MCI) or Alzheimer disease (AD). We examined cortical thickness and tissue density in monolingual and multilingual MCI and AD patients matched (within Diagnosis Groups) on demographic and cognitive variables. In medial temporal disease-related (DR) areas, we found higher tissue density in multilingual MCIs versus monolingual MCIs, but similar or lower tissue density in multilingual AD versus monolingual AD, a pattern consistent with cognitive reserve in AD. In areas related to language and cognitive control (LCC), both multilingual MCI and AD patients had thicker cortex than the monolinguals. Results were largely replicated in our native-born Canadian MCI participants, ruling out immigration as a potential confound. Finally, multilingual patients showed a correlation between cortical thickness in LCC regions and performance on episodic memory tasks. Given that multilinguals and monolinguals were matched on memory functioning, this suggests that increased gray matter in these regions may provide support to memory functioning. Our results suggest that being multilingual may contribute to increased gray matter in LCC areas and may also delay the cognitive effects of disease-related atrophy.

Hilary D Duncan, Jim Nikelski, Randi Pilon, Jason Steffener, Howard Chertkow, Natalie A Phillips

Concordia University material
Neuropsychologia abstract

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