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Can bilingualism protect the brain even with early stages of dementia?

A study led by York University psychology researchers provides new evidence that bilingualism can delay symptoms of dementia.

Alzheimer’s disease is the most common form of dementia, making up 60 to 70 per cent of dementia cases. Of all activities with neuroplastic benefits, language use is the most sustained, consuming the largest proportion of time within a day. It also activates regions across the entire brain. Ellen Bialystok, Distinguished Research Professor in York’s Department of Psychology, Faculty of Health, and her team tested the theory that bilingualism can increase cognitive reserve and thus delay the age of onset of Alzheimer’s disease symptoms in elderly patients. Bialystok’s team collaborated with researchers at Baycrest Health Sciences’ Rotman Research Institute, where Bialystok is an associate scientist.

Their study is believed to be the first to investigate conversion times from mild cognitive impairment to Alzheimer’s disease in monolingual and bilingual patients. Although bilingualism delays the onset of symptoms, Bialystok says, once diagnosed, the decline to full-blown Alzheimer’s disease is much faster in bilingual people than in monolingual people because the disease is actually more severe.

“Imagine sandbags holding back the floodgates of a river. At some point the river is going to win,” says Bialystok. “The cognitive reserve is holding back the flood and at the point that they were when they were diagnosed with mild cognitive impairment they already had substantial pathology but there was no evidence of it because they were able to function because of the cognitive reserve. When they can no longer do this, the floodgates get completely washed out, so they crash faster. Yet they had more time to enjoy the dry land.”

In the five-year study, researchers followed 158 patients from the Sam and Ida Ross Memory Clinic at Baycrest Health Sciences who had been diagnosed with mild cognitive impairment. The patients had been diagnosed after extensive testing and evaluation conducted by the clinic.

For the study, researchers classified bilingual people as having high cognitive reserve and monolingual people as having low cognitive reserve. Patients were matched on age, education, and cognitive level at the time of diagnosis of mild cognitive impairment. The researchers followed their six-month interval appointments at the clinic to see the point at which diagnoses changed from mild cognitive impairment to Alzheimer’s disease. The conversion time for bilinguals, 1.8 years after initial diagnosis, was significantly faster than it was for monolinguals, who took 2.6 years to convert to Alzheimer’s disease. This difference suggests that bilingual patients had more neuropathology at the time they were diagnosed with mild cognitive impairment than the monolinguals, even though they presented with the same level of cognitive function.

These results contribute to the growing body of evidence showing that bilinguals are more resilient in dealing with neurodegeneration than monolinguals. They operate at a higher level of functioning because of the cognitive reserve, which means that many of these individuals will be independent longer, Bialystok says. This study adds new evidence by showing that the decline is more rapid once a clinical threshold has been crossed, presumably because there is more disease already in the brain.

“Given that there is no effective treatment for Alzheimer’s or dementia, the very best you can hope for is keeping these people functioning so that they live independently so that they don’t lose connection with family and friends. That’s huge.”

The study was published in Alzheimer Disease and Associated Disorders.

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Telomeres are the protective caps of our chromosomes and play a central role in the ageing process. Shorter telomeres are associated with chronic diseases and high stress levels can contribute to their shortening. A new study now shows that if telomeres change in their length, that change is also reflected in our brain structure. This association was identified by a team of scientists including Lara Puhlmann and Pascal Vrtička from the Max Planck Institute for Cognitive Brain Sciences in Leipzig together with Elissa Epel from the University of California and Tania Singer from the Social Neuroscience Lab in Berlin as part of Singer’s ReSource Project. 

Telomeres are protective caps at the ends of chromosomes that become shorter with each cell division. If they become so short that the genes they protect could be damaged, the cell stops dividing and renewing. Consequently, the cell is increasingly unable to perform its functions. This mechanism is one of the ways in which we age.

Telomere length is therefore regarded as a marker for the biological age of a person — in contrast to their chronological age. For two people of the same chronological age, the person with shorter telomeres has an increased risk of developing age-related diseases such as Alzheimer’s or cancer, and even a shorter life expectancy.

Telomere lengthening

One key to staying younger longer therefore seems to be related to the question: How do we slow down, stop, or even reverse the shortening of telomeres? Genetics and unhealthy lifestyle are important contributors to telomere shortening, along with psychological stress. Based on this knowledge, researchers have examined how much lifestyle can influence telomere length. Recent studies suggest that telomeres can change faster than previously thought, possibly taking just one to six months of mental or physical training to elongate. The exciting premise is that telomere lengthening may represent a reversal of biological aging processes. However, it remains unclear if telomere elongation actually reflects any improvement in a person’s overall health and aging trajectory.

“To explore whether a short-term change in telomere length, after only a few months, might actually be associated with changes in a person’s biological age, we linked it to another biomarker of aging and health: brain structure,” explains Lara Puhlmann, now a member of the Research Group ‘Social Stress and Family Health’ led by Veronika Engert at the Leipzig Max Planck Institute. The project had been initiated by Tania Singer as part of the ReSource Project.

Participants of the researchers’ study underwent four MRI examinations, each spaced three months apart, and provided blood samples on the same dates. Using the DNA of leukocytes from the blood, the scientists were able to determine telomere length using a polymerase chain reaction. The MRI scans were used to calculate the thickness of the cerebral cortex of each participant. This outer layer of grey matter becomes thinner with age. It is also known that some neurological and age-related diseases are associated with faster cortical thinning in certain brain regions.

Fast changes in biological aging

The result: “Across systems, our biological aging appears to change more quickly than we thought. Indices of aging can vary together significantly in just three months,” says Puhlmann. If the telomeres changed in length, this was associated with structural changes in the brain. In a period when participants’ telomeres lengthened during the study, it was also more likely that their cortex had thickened at the same time. On the other hand, telomere shortening was associated with reductions of grey matter. This association occurred specifically in a brain region called the precuneus, which is a central metabolic and connectional hub.

The above results suggest that even short-term changes in telomere length over just three months might reflect general fluctuations in the body’s health- and aging status. Many other questions, however, remain open. “We do not know, for example, which biological mechanism underlies the short-term changes in telomere length”, explains the scientist, “or whether the short-term changes really have a longer-term effect on health.”

Mental training

At the same time, the team of researchers investigated whether telomere length could be altered by nine months of mindfulness- and empathy-based mental training, and whether such systematic change in telomere length would also be reflected in cortical thickening or thinning. Previous data from the ReSource Project, which was supported by the European Research Council (ERC), had already shown that certain regions of the cortex can be thickened by training, depending on the respective mental training contents of three distinct modules, each lasting for three months. The physiological stress response could also be reduced by mental training with social aspects.

In contrast to their earlier work and previous findings from other groups, the team did not find any training effects on telomeres. Future studies will need to continue to address the question of which measures or behaviors most effectively stop or even reverse telomere shortening, and the biological aging process.

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Reduced blood capillaries in the back of the eye may be a new, noninvasive way to diagnose early cognitive impairment, the precursor to Alzheimer’s disease in which individuals become forgetful, reports a newly published Northwestern Medicine study.

Scientists detected these vascular changes in the human eye non-invasively, with an infrared camera and without the need for dyes or expensive MRI scanners. The back of the eye is optically accessible to a new type of technology (OCT angiography) that can quantify capillary changes in great detail and with unparalleled resolution, making the eye an ideal mirror for what is going on in the brain.

“Once our results are validated, this approach could potentially provide an additional type of biomarker to identify individuals at high risk of progressing to Alzheimer’s,” said Dr. Amani Fawzi, a professor of ophthalmology at Northwestern University Feinberg School of Medicine and a Northwestern Medicine physician. “These individuals can then be followed more closely and could be prime candidates for new therapies aimed at slowing down the progression of the disease or preventing the onset of the dementia associated with Alzheimer’s.”

Therapies for Alzheimer’s are more effective if they are started before extensive brain damage and cognitive decline have occurred, added Fawzi, the Cyrus Tang and Lee Jampol Professor of Ophthalmology.

The study was published in PLOS ONE.

It’s known that patients with Alzheimer’s have decreased retinal blood flow and vessel density but it had not been known if these changes are also present in individuals with early Alzheimer’s or forgetful mild cognitive impairment who have a higher risk for progressing to dementia.

Multicenter trials could be implemented using this simple technology in Alzheimer’s clinics. Larger datasets will be important to validate the marker as well as find the best algorithm and combination of tests that will detect high-risk subjects, said Sandra Weintraub, a co-author and professor of neurology and of psychiatry and behavioral sciences at Feinberg.  

Weintraub and her team at the Northwestern Mesulam Center for Cognitive Neurology and Alzheimer’s Disease recruited 32 participants who had cognitive testing consistent with the forgetful type of cognitive impairment, and age-, gender- and race- matched them to subjects who tested as cognitively normal for their age. All individuals underwent the eye imaging with OCT angiography. The data were analyzed to identify whether the vascular capillaries in the back of the eye were different between the two groups of individuals.

Now the team hopes to correlate these findings with other more standard (but also more invasive) types of Alzheimer’s biomarkers as well as explore the longitudinal changes in the eye parameters in these subjects.

“Ideally the retinal findings would correlate well with other brain biomarkers,” Fawzi said. “​Long-term studies are also important to see if the retinal capillaries will change more dramatically in those who progressively decline and develop Alzheimer’s dementia.“

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Brains, brains, brains. One thing we’ve learned at NPR Ed is that people are fascinated by brain research. And yet it can be hard to point to places where our education system is really making use of the latest neuroscience findings.

But there is one happy nexus where research is meeting practice: bilingual education. “In the last 20 years or so, there’s been a virtual explosion of research on bilingualism,” says Judith Kroll, a professor at the University of California, Riverside.

Again and again, researchers have found, “bilingualism is an experience that shapes our brain for a lifetime,” in the words of Gigi Luk, an associate professor at Harvard’s Graduate School of Education.

At the same time, one of the hottest trends in public schooling is what’s often called dual-language or two-way immersion programs.

Traditional programs for English-language learners, or ELLs, focus on assimilating students into English as quickly as possible. Dual-language classrooms, by contrast, provide instruction across subjects to both English natives and English learners, in both English and in a target language.

The goal is functional bilingualism and biliteracy for all students by middle school.

New York City, North Carolina, Delaware, Utah, Oregon and Washington state are among the places expanding dual-language classrooms.

The trend flies in the face of some of the culture wars of two decades ago, when advocates insisted on “English first” education. Most famously, California passed Proposition 227 in 1998. It was intended to sharply reduce the amount of time that English-language learners spent in bilingual settings.

Proposition 58, passed by California voters on Nov. 8, largely reversed that decision, paving the way for a huge expansion of bilingual education in the state that has the largest population of English-language learners.

Some of the insistence on English-first was founded in research produced decades ago, in which bilingual students underperformed monolingual English speakers and had lower IQ scores.

Today’s scholars, like Ellen Bialystok at York University in Toronto, now say that research was “deeply flawed.”

“Earlier research looked at socially disadvantaged groups,” agrees Antonella Sorace at the University of Edinburgh, in Scotland. “This has been completely contradicted by recent research” that compares more similar groups to each other.

So what does recent research say about the potential benefits of bilingual education? NPR Ed called up seven researchers in three countries — Sorace, Bialystok, Luk, Kroll, Jennifer Steele, and the team of Wayne Thomas and Virginia Collier — to find out.

Attention

It turns out that, in many ways, the real trick to speaking two languages consists in managing not to speak one of those languages at a given moment — which is fundamentally a feat of paying attention.

Saying “Goodbye” to mom and then “Guten tag” to your teacher, or managing to ask for a crayola roja instead of a red crayon, requires skills called “inhibition” and “task switching.” These skills are subsets of an ability called executive function.

People who speak two languages often outperform monolinguals on general measures of executive function. “[Bilinguals] can pay focused attention without being distracted and also improve in the ability to switch from one task to another,” says Sorace.

Do these same advantages accrue to a child who begins learning a second language in kindergarten instead of as a baby? We don’t yet know. Patterns of language learning and language use are complex. But Gigi Luk at Harvard cites at least one brain-imaging study on adolescents that shows similar changes in brain structure when compared with those who are bilingual from birth, even when they didn’t begin practicing a second language in earnest before late childhood.

Empathy

Young children being raised bilingual have to follow social cues to figure out which language to use with which person and in what setting. As a result, says Sorace, bilingual children as young as age 3 have demonstrated a head start on tests of perspective-taking and theory of mind — both of which are fundamental social and emotional skills.

Reading (English)

About 10 percent of students in the Portland, Ore., public schools are assigned by lottery to dual-language classrooms that offer instruction in Spanish, Japanese or Mandarin, alongside English.

Jennifer Steele at American University conducted a four-year, randomized trial and found that these dual-language students outperformed their peers in English-reading skills by a full school year’s worth of learning by the end of middle school.

Such a large effect in a study this size is unusual, and Steele is currently conducting a flurry of follow-up studies to tease out the causality: Is this about a special program that attracted families who were more engaged? Or about the dual-language instruction itself?

“If it’s just about moving the kids around,” Steele says, “that’s not as exciting as if it’s a way of teaching that makes you smarter.”

Steele suspects the latter. Because the effects are found in reading, not in math or science where there were few differences, she suggests that learning two languages makes students more aware of how language works in general, aka “metalinguistic awareness.”

The research of Gigi Luk at Harvard offers a slightly different explanation. She has recently done a small study looking at a group of 100 fourth-graders in Massachusetts who had similar reading scores on a standard test, but very different language experiences.

Some were foreign-language dominant and others were English natives. Here’s what’s interesting. The students who were dominant in a foreign language weren’t yet comfortably bilingual; they were just starting to learn English. Therefore, by definition, they had much weaker English vocabularies than the native speakers.

Yet they were just as good at decoding a text.

“This is very surprising,” Luk says. “You would expect the reading comprehension performance to mirror vocabulary — it’s a cornerstone of comprehension.”

How did the foreign-language dominant speakers manage this feat? Well, Luk found, they also scored higher on tests of executive functioning. So, even though they didn’t have huge mental dictionaries to draw on, they may have been great puzzle-solvers, taking into account higher-level concepts such as whether a single sentence made sense within an overall story line.

They got to the same results as the monolinguals, by a different path.

School performance and engagement.

Wayne Thomas and Virginia Collier, a husband and wife team of professors emeritus at George Mason University in Virginia, have spent the past 30 years collecting evidence on the benefits of bilingual education.

“Wayne came to our research with skepticism, thinking students ought to get instruction all day in English,” says Virginia Collier. “Eight million student records later, we’re convinced,” Wayne Thomas chimes in.

In studies covering six states and 37 districts, they have found that, compared with students in English-only classrooms or in one-way immersion, dual-language students have somewhat higher test scores and also seem to be happier in school. Attendance is better, behavioral problems fewer, parent involvement higher.

Diversity and integration.

American public school classrooms as a whole are becoming more segregated by race and class. Dual-language programs can be an exception. Because they are composed of native English speakers deliberately placed together with recent immigrants, they tend to be more ethnically and socioeconomically balanced. And there is some evidence that this helps kids of all backgrounds gain comfort with diversity and different cultures.

Several of the researchers I talked with also pointed out that, in bilingual education, non-English-dominant students and their families tend to feel that their home language is heard and valued, compared with a classroom where the home language is left at the door in favor of English.

This can improve students’ sense of belonging and increase parent involvement in their children’s education, including behaviors like reading to children.

“Many parents fear their language is an obstacle, a problem, and if they abandon it their child will integrate better,” says Antonella Sorace of the University of Edinburgh. “We tell them they’re not doing their child a favor by giving up their language.”

Protection against cognitive decline and dementia.

File this away as a very, very long-range payoff. Researchers have found that actively using two languages seems to have a protective effect against age-related dementia — perhaps relating to the changes in brain structure we talked about earlier.

Specifically, among patients with Alzheimer’s in a Canadian study, a group of bilingual adults performed on par with a group of monolingual adults in terms of cognitive tests and daily functioning. But when researchers looked at the two groups’ brains, they found evidence of brain atrophy that was five to seven years more advanced in the bilingual group. In other words, the adults who spoke two languages were carrying on longer at a higher level despite greater degrees of damage.

The coda, and a caution

One theme that was striking in speaking to all these researchers was just how strongly they advocated for dual-language classrooms.

Thomas and Collier have advised many school systems on how to expand their dual-language programs, and Sorace runs “Bilingualism Matters,” an international network of researchers who promote bilingual education projects.

This type of advocacy among scientists is unusual; even more so because the “bilingual advantage hypothesis” is being challenged once again. A review of studies published last year found that cognitive advantages failed to appear in 83 percent of published studies, though in a separate meta-analysis, the sum of effects was still significantly positive.

One potential explanation offered by the researchers I spoke with is that advantages that are measurable in the very young and very old tend to fade when testing young adults at the peak of their cognitive powers.

And, they countered that no negative effects of bilingual education have been found. So, they argue that even if the advantages are small, they are still worth it.

Not to mention one obvious, outstanding fact underlined by many of these researchers: “Bilingual children can speak two languages! That’s amazing,” says Bialystok.

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