Bilingual, Debby Burke Study, Alzheimer's
Debby Burke, Cog Sci, Linguistics, Faculty

Deborah M. Burke, W.M. Keck Distinguished Service Professor and Professor of Linguistics and Cognitive Science
 

In the U.S. alone, an estimated 5.5 million people – the vast majority of them age 65 and over – live with Alzheimer’s disease, and the number is expected to continue to grow. The debilitating disease takes a toll on the patient as well as the caregiver, and deaths from the disease have increased by 89 percent since 2000.

Some drugs are approved to ease some symptoms of Alzheimer’s, but so far, there is no pharmacological treatment that has been successful in delaying the onset of Alzheimer’s disease.

Deborah Burke, W.M. Keck Distinguished Service Professor of linguistics and cognitive science at Pomona College, argues in the co-authored study, Aging in Two Languages: Implications for Public Health, that learning a second language can delay the onset of Alzheimer’s disease by four to five years. Burke, who researches the cognitive and neural processes involved in language, discusses the implications of bilingualism on cognitive function and the potential ramifications on savings in healthcare costs over the long-term.

What is the effect of bilingualism on cognitive functions?

Bilingual children typically show some delay in acquiring vocabulary and reading compared to monolinguals, which is unsurprising given that these skills must be acquired in two different languages.

However, other cognitive functions benefit significantly from bilingualism, most notably the control of attention. Bilingual children and adults are better at focusing attention than monolinguals, demonstrating a superior ability to direct attention to target information and ignore distractions, an essential cognitive process called executive control. In normal aging during adulthood, there is a reduction in executive control but this decline is reduced in bilinguals compared to monolinguals.

Evidence suggests that bilinguals’ repeated switching between languages requires suppression of one language and focus on the other; repeating this process many times a day appears to strengthen executive control. As would be expected, we also see effects of bilingualism on the brain: Compared to monolinguals, bilinguals show increased density of grey matter in neural areas associated with executive control.

Does bilingualism affect pathological aging in the onset of Alzheimer’s disease?

Studies of bilinguals and monolinguals diagnosed with Alzheimer’s disease show quite stunning differences in the progression of the disease in these two groups. A number of recent studies report that the age of diagnosis of Alzheimer’s disease is four to five years older for bilinguals than monolinguals. This delay in the onset of the disease in bilinguals has been found in both literate and illiterate people and in monolingual and bilingual countries across the world, including the United States, India and Belgium. Moreover, studies that follow large groups of people over time to monitor for onset of mild cognitive impairment (MCI), a precursor of Alzheimer’s disease, report that the incidence of MCI was lower for bilinguals than monolinguals and the incidence decreased as the number of languages spoken increased.

These effects of bilingualism are especially significant because no pharmacological treatment has been successful in delaying the onset of Alzheimer’s disease. Although there are drugs approved to ease some symptoms of Alzheimer’s, they do not affect the progression of the disease.

If someone learns a second language as an adult, will they see the same benefits?

The older a person is when they acquire a second language, the lower their proficiency is likely to be.  Unfortunately, in the research reporting this result the upper age limit is young adulthood, often college seniors. What’s needed now is research investigating the benefits of second language acquisition at age 50 years and older.  We do know that the beneficial effect of bilingualism results from the consistent use of both languages which requires switching attention back and forth between the two languages. So the beneficial effect on attentional processes is likely to depend on consistent use of both languages. This suggests that adults who learn a second language should alternate as much as possible between their two languages to accrue the maximum positive effect on their executive processes.

If Alzheimer’s disease and dementia can be delayed, what are the potential implications for healthcare costs?

The global population is aging and this highlights the urgency of developing interventions that effectively delay mild cognitive impairment (MCI) and the progression to Alzheimer’s disease.  Alzheimer’s is the third most costly disease in the U.S., following heart disease and cancer, with costs estimated to exceed $100 billion per year. There is also an enormous mental and physical burden on the caretaker.

The Alzheimer’s Association estimates that the number of new cases will increase by almost 50 percent from 2010 to 2030. This highlights the urgency of pharmacological or experiential interventions that would reduce the progression of the disease.  There is currently no effective drug treatment that slows the progression of MCI to Alzheimer’s disease or slows the progression of Alzheimer’s. There is, however, good evidence that bilingualism delays the onset of Alzheimer’s by four to five years.  It has been estimated that a delay in the onset of Alzheimer’s for five years would result in a 41 percent reduction of cases and 40 percent lower medical costs of Alzheimer’s disease in 2050.