The Story That "Bilinguals Have Healthier Brains" Might Not Be Accurate: A Researcher's Critique

For years, the story sounded clear: speak 2 languages = better brain health. It seemed like established knowledge. But a new critique casting doubt on this claim comes from a surprising source: Prof. Arturo Hernandez, a psychologist at the University of Houston. He argues that the conclusions of popular studies on "multilingualism protects the brain" go further than the data allows, and make a fundamental mistake: they confuse correlation with causation. Yes, multilingual regions show better brain aging. But not necessarily because of the languages. Because of something else.

The Existing Story: Languages Protect the Brain

Classic studies on bilingualism and cognition began as early as the 1960s (Peal & Lambert, 1962), but the modern line of the "bilingual advantage" crystallized mainly in the mid-2000s. In 2007, a pivotal study by Ellen Bialystok was published: speakers of 2 languages developed dementia about 4 years later than monolingual speakers.

The theoretical explanation: cognitive reserve. The idea is that when the brain maintains two languages over the years, it builds neural infrastructure and compensatory ability. When aging takes its toll, there is a buffer.

In 2025, a large study was published in Nature Aging (Amoruso et al.) that strengthened the story: based on data from 86,149 participants from 27 European countries, multilingualism was associated with about half the risk of accelerated aging. This became a headline in the global press.

Hernandez's Critique

Hernandez published a critique in Brain and Language where he does not dispute the data itself, but rather its interpretation. He points to a critical confounding variable: the multilingual countries in Europe are often also the wealthier ones, with the best access to healthcare and the highest life expectancy. In his words: "We examined the data closely and argued that the study's conclusions go further than the data can support."

"A gap of 6 years in life expectancy is unlikely to be explained by language. World-class healthcare, better nutrition in early childhood, higher occupational safety, and lower chronic stress offer a much simpler and more plausible explanation."

The Example Hernandez Presents

To illustrate the problem, Hernandez points to the gap between multilingual countries and relatively monolingual countries on the same continent:

• Life expectancy in Luxembourg (multilingual): about 82.5 years
• Life expectancy in the Netherlands (multilingual): about 82.5 years
• Life expectancy in Bulgaria (less multilingual): about 75.8 years
• Life expectancy in Romania (less multilingual): about 76.3 years
• A gap of about 6 to 7 years. According to Hernandez, such a gap is much better explained by differences in healthcare, nutrition, and economic inequality, rather than by the languages themselves.

When such structural variables are taken into account, Hernandez argues, the apparent language effect weakens significantly.

Why This Matters: The Picture Is Not Clear-Cut

Hernandez's critique fits into a long-standing skeptical line in the field. Researchers like Angela de Bruin, Kenneth Paap, and Minna Lehtonen have pointed over the years to replication failures and null results: quite a few studies that directly compared bilinguals and monolinguals, especially when controlling for education and socioeconomic background, did not find the promised "bilingual advantage."

It is also possible that the direction of the relationship depends on context: in some countries, bilingualism may be a sign of higher education and wealth, and in other contexts, a sign of a challenging socioeconomic status (e.g., immigrants who need to manage in two languages). In both cases, language is not necessarily the cause, but a marker of something else.

So Learning a Second Language Doesn't Help?

No. Hernandez does not claim that. He claims the effect has been overstated. It is possible that learning a language helps to some extent, but probably not to the degree commonly presented. Other factors, such as formal education, physical activity, and social network, are much stronger.

The important point: Don't live as if multilingualism alone is enough to protect your brain. Even if you speak 5 languages, if you don't exercise, your diet is poor, and you don't sleep, your brain will age quickly.

The "Correlation and Causation" Problem in All Health Studies

Hernandez's critique is an example of a broader problem in aging research. When studies rely on "people who do X live longer," they don't always distinguish between:

• X causes longevity: the desired explanation
• X is linked to longevity due to a common factor: e.g., wealthy people both do X and live longer
• Longevity causes X: e.g., people who live longer have time to learn languages

Many "anti-aging" recommendations are based on the second type of relationship. One should always ask: Why do people who do X also live longer? Is it them, or are they just more similar to the "average healthy older adult"?

How to Really Test It?

The only real proof that "X causes longevity" is a randomized clinical trial. Example: take 1,000 monolinguals, randomly assign half to learn a second language for 5 years, and half not. If after 30 years the first group is healthier, that's proof.

The problem: such trials are almost never conducted because they require decades. Most of what we "know" about aging is based on statistical associations alone.

So What Is Known with Higher Certainty?

Actions with stronger evidence than multilingualism:

• Regular physical activity: controlled trials show a significant effect
• Mediterranean diet: the PREDIMED trial (Spain) showed a risk reduction of about 30% for cardiovascular events
• Avoiding smoking: trials on smoking cessation show improvement
• Quality sleep: studies on treating sleep disorders
• Blood pressure treatment: the SPRINT-MIND trial showed a reduction in risk for mild cognitive impairment and dementia

And Still, Is Learning a Language Worth It?

Absolutely. Even if the effect on the brain is smaller than promised, there are real benefits:

• A new language is a cognitive challenge that builds something
• Opening a door to cultural life
• Access to information in its original form
• New friends from other cultures

But don't rely on it alone. Combine it with the stronger interventions.

The Bottom Line

Hernandez is not trying to ruin the nice story. He is trying to correct it. Multilingualism is not harmful to the brain, but it is probably not the magic that is told about. When studies spin your head with "if only you do X, you'll live forever," remember that not every statistical association equals causation. Ask for the controlled trial. In the case of multilingualism, it is still missing. This is a cautionary reminder for all the promises in the anti-aging world.