Can Learning A New Language Protect Against Dementia? What We Do and Don’t Know So Far

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You’ve probably heard the claim that speaking multiple languages can help to keep your brain healthy and protect against neurodegenerative diseases like Alzheimer’s. We’ve previously reported on studies that suggest as much, but suppose you decided to start learning a new language tomorrow, with the hope of improving your cognitive function and staving off dementia. How justified would you be in doing so, considering the evidence that we currently have?

Our best evidence comes from studies comparing monolinguals (those who speak one language) to bilinguals. There is no universally agreed definition of bilingualism, but it implies at least a high level of fluency in two languages and, in some definitions, equal mastery of two languages. Bilingualism usually occurs when children are exposed to multiple languages growing up, though adults can also become bilingual. Today, over half of the world’s population is fluent in two or more languages.

So what does this research tell us? Studies comparing bilinguals and monolinguals with dementia generally find that bilinguals develop symptoms of Alzheimer’s disease 4 to 7 years later than their monolingual counterparts. However, once symptoms begin, the disease doesn’t necessarily progress any slower in bilinguals.

It is important to be aware that these studies are associative in nature: rather than introducing a change and observing the consequences of that change, they look instead at the association between two pre-existing variables. This means that they can’t definitively say that bilingualism itself directly causes a delay in the onset of dementia. Consider the fact that a bilingual has more potential friends to make, more media to consume, more cultures to experience, and the impact that these factors could have on the brain. With that being said, if this relationship is causal, are there any mechanisms that could explain it?

Unfortunately, there is still much about neurodegenerative disease and the brain in general that is poorly understood, making the proposal of a precise mechanism challenging. One theory is based on ‘cognitive reserve‘ – the idea that some people are more resilient to neurological damage because their brains are able to recruit alternative networks to compensate for those that have been damaged. In the case of bilinguals, it may be that the additional brain resources required to maintain two languages, constantly ‘suppressing’ one of them, increases this cognitive reserve.

Studies suggest that bilinguals are also better at various other cognitive tasks, such as following complex instructions, switching to new instructions, multitasking, and the Stroop Test, in which the participant must name the colour that words are written in and avoid reading the word itself. Interestingly, bilinguals may also have smaller vocabularies on average, and take longer to retrieve words from memory.

Unfortunately, studies are not consistent in the nature of the benefits gained from bilingualism. For example, one study only found benefit when more than two languages were spoken, while another reported no significant benefit beyond the first language. One study also reported that Alzheimer’s disease was not affected, but that mild cognitive impairment was – though the weight of the evidence does still support a benefit for Alzheimer’s.

This is not necessarily an indication that bilingualism isn’t beneficial after all, but rather that there may be different types and different degrees of bilingualism upon which the benefits of knowing a second language depend. One idea that looks to be gaining traction is that active bilingualism may be necessary. This is to say that simply knowing a second language is not enough, but that both languages must also be used on a regular basis.

So let’s now return to our original question: should the goal of bettering your brain factor in to your decision to learn a second language? There’s no definite answer yet, but consider the following: firstly, it’s not certain what level of fluency is required in order for significant benefits to be gained. You might not have to be truly bilingual, but being able to introduce yourself and count to ten in Spanish probably isn’t going to cut it. Secondly, you probably need to use your second language in some capacity every day, which might be challenging depending on where you live.

In summary, being able to speak multiple languages is an incredibly valuable skill, but you probably need to be quite proficient and active with your second languages in order to receive any cognitive benefits. Simply staying cognitively active in other ways, physical exercise, and healthy eating are probably more feasible and effective strategies for keeping your brain healthy.