Summary: In a study of Alzheimer’s patients, those who spoke two or more languages fluently developed symptoms about four years later, on average, than monolingual individuals.
Source: UCLA
Overview: Researchers reviewing 253 patients with probable Alzheimer’s disease found that individuals who used two languages proficiently showed a delay of roughly four years in the appearance of clinical dementia symptoms compared with monolingual patients. Published February 11 in the journal Dementia & Geriatric Cognitive Disorders, the study supports the idea that regular use of two languages builds cognitive reserve that helps mask or compensate for Alzheimer’s-related decline.
“Here in Los Angeles County, we have one of the most bilingual populations in the country,” said Mario Mendez, MD, PhD, Director of Neurobehavior at the VA Greater Los Angeles and Professor of Neurology and Psychiatry at the David Geffen School of Medicine at UCLA, who led the study. Many patients speak their native language at home while using English in public and professional settings. Among the bilingual participants the most common native languages were Farsi and Spanish, with more than a dozen other languages also represented.
Mendez noted that the roughly four-year delay is consistent with findings from similar retrospective studies in Canada, India, Taiwan and elsewhere. The repeated observation across diverse populations suggests that the protective effect arises from bilingual brain use rather than from some external cultural influence.
Importantly, bilingualism does not prevent the underlying biological changes of Alzheimer’s disease. Rather, habitual management of two languages appears to help people function well for longer, despite accumulating brain pathology. “They are developing the disease, but they aren’t showing clinical symptoms or impairment until later,” Mendez said.
Using two languages requires continuous selection of the appropriate language and suppression of the other, a form of cognitive control often called code-switching. Those processes engage frontal brain regions responsible for executive functions such as working memory, emotional control and inhibition. Frequent exercise of these networks may strengthen neural connections and provide resilience against the clinical expression of dementia.
Interestingly, caregivers reported that as dementia progressed most bilingual patients tended to revert to exclusive use of their first language. “Are they having trouble inhibiting their native language?” Mendez asked. With intact executive control, people can choose the appropriate language for the context; as executive function declines in dementia, that ability diminishes and the dominant early-learned language often resurfaces.
One notable implication is that second-language proficiency, even when acquired later in life, appears beneficial. Many study participants learned English after immigrating, well after acquiring their native language. “Your proficiency in using the second language is more important than whether you learned it before age five,” Mendez said.
Mendez plans further research to characterize the speech and cognitive features of people who display this resilience. He aims to determine whether stronger executive function or particular linguistic patterns explain their preserved functioning and delayed clinical decline.
Learning a new language and adapting to a different culture is challenging, but if sustained bilingual use builds cognitive reserve and delays dementia symptoms by several years, the effort could offer substantial long-term benefit. “There are good things about getting acculturated,” Mendez observed. “If it delays dementia by four years, that’s a significant difference.”
Neuroscience News would like to thank Caroline Seydel from UCLA for submitting this research news.
About this neuroscience research article
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UCLA
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Caroline Seydel – UCLA
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Original Research: Closed access. “Bilingualism Delays Expression of Alzheimer’s Clinical Syndrome”. Mendez MF, Chavez D, Akhlaghipour G. Dementia and Geriatric Cognitive Disorders, doi: 10.1159/000505872.
Abstract
Bilingualism Delays Expression of Alzheimer’s Clinical Syndrome
Objective: To evaluate the effects of bilingualism on the emergence of Alzheimer’s clinical syndrome.
Background: Prior studies propose that managing two languages increases cognitive and neural reserve, which may delay the clinical expression of dementia.
Methods: In a clinic serving a large immigrant population, researchers identified 253 patients with probable Alzheimer’s disease supported by intermediate or high evidence of AD pathology. Records were reviewed for demographics, native language other than English, age at symptom onset and clinical presentation, Mini-Mental State Examination (MMSE), digit spans, verbal fluency, naming, and memory performance.
Results: Seventy-four patients (29.2%) were bilingual, representing languages such as Farsi, Spanish, Chinese, Tagalog and Arabic. Compared with the 179 monolingual patients, bilinguals showed a significant delay—about four years—in both age at symptom onset and age at clinical presentation (p = 0.003). This delay persisted even though bilinguals presented with lower MMSE scores. Other cognitive measures were similar across groups except for worse English naming among bilinguals. Caregiver reports indicated that 66 of the 74 bilingual patients (89.2%) gradually reverted to predominant use of their first language as dementia progressed.
Conclusions: Consistent with international reports, bilingualism was associated with delayed clinical expression of Alzheimer’s disease. Frequent reversion to the first learned language may provide a compensatory “back-up,” masking early symptoms or facilitating compensation among bilinguals.
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