March 7, 2011 — Compared with bilingual seniors, those who speak more than 2 languages appear to be protected from cognitive impairment according to a longitudinal study.

The results were released February 22 and will be presented at the upcoming American Academy of Neurology 63rd Annual Meeting in Honolulu, Hawaii.

The memory protection afforded by multilingualism appeared to occur regardless of whether the languages were currently or previously spoken, suggested lead study author Magali Perquin, PhD, with the Center for Health Studies from the Public Research Center for Health in Luxembourg.

Multilingual Population

The study included 230 subjects (57% female), with an average age of 73 years, who were invited randomly to participate in the Mémo Vie study, a longitudinal cohort study looking at cognition and risk factors in the elderly in Luxembourg.

After standardized neurogeriatric and neuropsychological evaluation, a total of 44 subjects (19%) were classified as having cognitive impairment, whereas the rest had normal cognition. People with dementia were excluded.

The number of languages spoken by the subjects ranged from 2 to 7, reflecting Luxembourg's multilingual population, the researchers note.

A generalized linear mixed model, which accounted for age and level of education, found a strong association between cognitive function and the number of languages fluently practiced — either currently or at any time of life.

Compared with bilingual subjects, those who spoke 3 languages were almost 4 times less likely to develop cognitive problems and those who spoke 4 or more languages were more than 5 times less likely to have cognitive impairment.

Table. Probability of Protection Against Cognitive Decline for Multi- vs Bilingualism

No. of Languages Odds Ratio (95% CI) 3 Languages 3.58 (1.13 – 11.37) 4 Languages 5.66 (1.48 – 21.59) >4 Languages 5.23 (1.11 – 24.53)

CI = confidence interval

"Further studies are needed to...determine whether the protection is limited to thinking skills related to language or if it also extends beyond that and benefits other areas of cognition," Dr. Perquin said in a press release from AAN.

Compensatory Mechanisms

Reached for comment on these preliminary data, Fergus Craik, PhD, confirmed that the benefits of multilingualism stretch beyond language-bound cognition.

"Laboratory tests have shown that the benefit is not just in language and memory but in other areas of executive control," said Dr. Craik, a senior scientist from the Department of Psychology at the Rotman Research Institute at Baycrest and the University of Toronto, Ontario, Canada.

Dr. Craik and his colleagues have recently published work showing that among 211 consecutive Alzheimer's patients, those who were bilingual (n = 102) had their diagnosis delayed by roughly 4 years compared with those who were unilingual (n = 109) (Neurology. 2010;75:1726-1729).

Further work by his group, which is not yet published but was presented last month at the meeting of the American Association for the Advancement of Science, shows that computed tomographic scans of Alzheimer's patients who are functioning at the same level show more advanced brain deterioration in the bilingual compared with the unilingual subjects.

"The language kind of pulls them back up to a higher level than they should have been on the basis of the amount of atrophy," said Dr. Craik in an interview.

Having a second language appears to give people cognitive reserve that somehow compensates for their brain atrophy, he explained. "So bilingualism doesn't simply protect the brain from deteriorating — the brain apparently does deteriorate but there are other factors that compensate."

"...there is actually a lot of evidence that both languages are always active in the brain at some level — and some kind of effort is needed — a kind of attentional control mechanism — to keep the unused language inhibited temporarily while you're using the first."

Dr. Craik says there are several theories about how multilingualism achieves this compensation. "There's a number of possibilities which we are currently trying to track down. It could be better blood supply, it could be more gray matter in other parts of the brain, or it could be more white matter — therefore better connectivity."

Whatever it is anatomically, he believes the benefit comes from having to "damp down the second language while you're using the first. A lot of studies show that although bilingual people feel, when they're speaking, that their other language is shut out, there is actually a lot of evidence that both languages are always active in the brain at some level — and some kind of effort is needed — a kind of attentional control mechanism to keep the unused language inhibited temporarily while you're using the first."

Dr. Perquin did not provide a disclosure statement. Her research was supported by the Fonds National de la Recherche Luxembourg. Dr. Craik serves as a consultant for the Ontario Innovation Trust; serves on the editorial boards of Psychology and Aging, Neuropsychology, Aging, Neuropsychology, and Cognition, and Memory; receives royalties from the publication of The Oxford Handbook of Memory (Oxford University Press, 2000) and Lifespan Cognition: Mechanisms of Change (Oxford University Press, 2006); and receives research support from the Canadian Institutes of Health Research, the Alzheimer Society of Canada, Natural Sciences and Engineering Research Council of Canada.

American Academy of Neurology (AAN) 63rd Annual Meeting: Abstract 3397. Released February 22, 2011, ahead of presentation.