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

For 30 years, the story was clear: speak 2 languages = better brain health. It sounds like valuable knowledge. But new research casting doubt on this claim comes from a surprising source: Prof. Arturo Hernandez, a psychologist at the University of Houston who himself speaks 3 languages. He argues that popular studies on "multilingualism protects the brain" made a fundamental mistake: they confused correlation with causation. Yes, multilingual regions show better brain aging. But not because of the languages. Because of something else.

The Existing Story: Languages Protect the Brain

Classic studies on bilingualism and cognition began in the 1960s. During the 2000s, they accumulated, and in 2007, a pivotal study was published: bilingual speakers developed dementia 4-5 years later than monolingual speakers.

The explanation: cognitive reserve. When your brain maintains two languages, it builds extra neural infrastructure. When aging takes its toll, you have a buffer.

In 2024, a large study published in Nature Aging reinforced the story: multilingual regions in Europe (like Luxembourg, the Netherlands, Switzerland) showed healthier brain aging compared to monolingual regions. This became a headline in the press.

Hernandez's Critique

Hernandez published a response in Brain and Language. He does not dispute the data. He disputes the interpretation. He points to a critical confounding variable: all the multilingual countries in Europe are also the wealthiest, with the most access to healthcare, and the highest life expectancy.

"A 6-year life expectancy gap is unlikely to be explained by language alone. Global health, excellent childhood nutrition, workplace safety, and lower stress offer a much more plausible explanation."

The Data Hernandez Presents

He examined the same data and found:

• Life expectancy in Luxembourg: 84 years
• Life expectancy in Albania: 78 years (also a multilingual region)
• If multilingualism were the cause, the gap would not be so large
• Healthcare spending per capita in Luxembourg: $6,000/year
• Healthcare spending in Albania: $350/year
• A 17-fold gap. Everything attributed to multilingualism is better explained by healthcare spending

Individual Studies: The Picture Is Not Clear-Cut

Additionally, Hernandez points out that individual studies on bilinguals in the U.S. or Canada have not always found the effect. In a 2018 study at Cambridge on 745 bilinguals in Canada, there was no significant cognitive difference compared to monolinguals with similar education.

Why? Possibly because bilingualism in the U.S./Canada is often a sign of lack of wealth (immigrants who need to speak their first language and the local language), not an advantage. While in Europe, bilingualism is often a sign of higher education and wealth.

So Learning a Second Language Doesn't Help?

No. Hernandez does not claim that. He claims the effect has been overstated. Learning a language may help a little, but not to the extent commonly presented. Other factors—formal education, physical activity, social network—are much stronger.

The key 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, have poor nutrition, and 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 do not 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. You should always ask: Why do people who do X also live longer? Is it them, or just that they are more like the "average healthy adult"?

How to Really Test It?

The only true 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 lives healthier, that's proof.

The problem: such trials do not exist because they require decades. Most of what we "know" about aging is based on statistical correlations alone.

So What Is Actually Known for Certain?

Actions with stronger evidence than multilingualism:

• Regular physical activity: controlled trials show a significant effect
• Mediterranean diet: PREDIMED trial (Spain) - 30% risk reduction
• Avoiding smoking: cessation trials show improvement
• Quality sleep: trials on sleep disorders
• Blood pressure treatment: SPRINT-MIND trial - reduced dementia

And Yet, Is Learning a Language Worth It?

Indeed! Even if the effect on the brain is smaller than promised, there are benefits:

• A new language is a cognitive challenge that builds something
• Opening up cultural life
• Access to information in the original
• 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 destroy the beautiful story. He is trying to correct it. Multilingualism does not harm the brain, but it is not the magic that stories make it out to be. When studies spin your head with "if only you do X, you'll live forever," remember that not every statistical correlation = causation. Ask for the controlled trial. In the case of multilingualism, there isn't one. This is a warning for all promises in anti-aging.