Research shows that speaking two languages can delay the onset of the disease by up to five years. Attracted by this potential benefit, many people, like my father, try to learn a new language as adults. According to a survey conducted by language learning app Memrise, 57% of users said “promoting brain health” was their motivation for using the program. But is this possible? Research on bilingualism and dementia has been conducted among people who have used multiple languages in their daily lives since at least early adulthood. Whether randomly learning another language after this would confer the same cognitive benefits is open to question.

How Bilingualism Benefits the Aging Brain

Many activities have been linked to improving brain health in older adults, such as more education at a younger age, physical activity, and hobbies that stimulate cognitive abilities. Experts say regularly speaking multiple languages may be particularly beneficial.

“We use language in every aspect of our daily lives, so the bilingual brain is constantly working,” said Marc Antonio, an associate professor at Western Sydney University in Australia who specializes in bilingualism. “That’s something you can’t do with other mind-enriching experiences, like playing an instrument.”

The age at which another language is learned appears to be less important than the frequency with which it is spoken, said Caitlin Weil, a research engineer who studies bilingualism and brain health at the Broca Hospital in Paris. “The cognitive benefit it brings is that you have to suppress your native language,” she said. If you try to recall the correct word in another language, your brain is forced to do so. “So if you use a second language regularly, you get this cognitive training.”

This process is called cognitive inhibition and is associated with better executive functioning. In theory, by improving these types of processes, the brain would be more resilient to damage caused by conditions such as dementia—a concept known as cognitive reserve. That is, the stronger your mental abilities are, the longer you can function normally, even if your brain health begins to decline.

In a landmark 2007 paper, Toronto researchers found that among people with dementia, bilingual people developed symptoms an average of four years later than non-bilingual people. Several studies published since have reported similar findings, although some others have found no such differences.

Learning in Later Life

For people in their 60s, the evidence for benefits from learning a second language is weaker.

The study by Antonio and colleagues found that Chinese adults aged 60 and older improved on cognitive tests after a six-month language learning program, but so did those who played Sudoku and crossword puzzles. Another small study found no change in cognitive scores among older Italians who took English classes for four months, but those who did not take English classes saw their scores decline. Two newer studies on the subject, published in 2023, found little difference in cognitive performance after participating in a language learning program.

The scientists who conducted the studies offer some possible explanations for this disappointing result. One is that the participants are very active volunteers who may already be performing at the top level of their peers, so it is difficult to see any improvement.

“We have to be careful when recruiting participants, are they representative of this population?” said Weir, who was involved in one of the experiments. “Are their cognitive levels a little too high?”
Another reason is that the duration of language intervention may be too short. Judith Grossman, who studied the topic during her PhD at the University of Heidelberg in Germany, said several studies of the issue have used language courses that “vary widely in length and frequency.” Some studies trained participants for eight months, and some studies only trained for one week.

To Antonio, these limited findings are not entirely surprising. No one, he said, would think that learning a new language for six months “is the same as using two languages for a lifetime.” But he does believe that language classes can improve cognitive abilities by stimulating the brain.

Perhaps more importantly, Grossman said, there are other potential advantages to learning another language, such as traveling or connecting with a new community. For example, my father remained a pen pal with his first governess after she moved back to Paris, and he made many trips to France (and French-speaking Canada).

Today, at the age of 76, he remains as sharp as ever.