The risk of dementia rises as the brain ages. One reason is that connections between brain cells weaken over time. Diseases of the brain, such as Alzheimer’s and stroke, can speed this up, eventually leading to dementia, a loss of mental abilities and a loss of independence.
Scientists can now estimate a person’s brain age from brain scans, and compare it with their actual age. This difference, known as the brain-age gap, can predict who is more likely to see faster mental decline and go on to develop dementia. One study followed around 39,000 people and found exactly that link. The good news is that lifestyle changes – stopping smoking, drinking less alcohol and exercising regularly – can slow this decline.
But what about learning another language? Could that help keep the brain younger for longer and delay dementia?
Preliminary findings presented at a recent scientific conference suggested that people who speak more languages tend to have younger brains. Speaking two languages was linked to a six-year delay in brain ageing, and speaking four languages was linked to a delay of up to 13 years.
A separate study of more than 86,000 people across 27 European countries found that people who spoke only one language were more than twice as likely to show faster brain ageing. Speaking two languages cut that risk by 30%, according to the findings.
The theory is that learning languages builds what scientists call brain reserve – extra connections between nerve cells that help the brain withstand the damage caused by ageing and disease.
But the picture may not be so simple. It could depend on how the research is done, who is being studied, and why someone speaks more than one language in the first place.
Delayed diagnosis, not lower risk
When researchers combined the results of several studies, they found that speaking more than one language didn’t actually lower a person’s risk of developing dementia. What it did do was delay diagnosis by two to five years.
One explanation is that learning another language builds vocabulary and problem-solving skills, which may help hide the early signs of dementia rather than prevent the disease itself.
There’s another complication. Most studies on this topic have focused on white, middle-class people in the US and Europe – people who often grew up speaking several languages thanks to a good education and supportive parents.
This same group is also more likely to do other things that protect the brain, such as reading for pleasure, playing sport or learning a musical instrument, all of which have been linked to a lower risk of dementia.
There’s also a chicken-and-egg problem. People with good memories for words and language rules – and the support and motivation to use them – may simply be more likely to become multilingual in the first place.
And being middle class generally means a healthier lifestyle: better food, better healthcare, more time for leisure and less stress – all of which reduce dementia risk on their own.
Why migrants don’t fit the pattern
If speaking multiple languages were simply protective, you’d expect migrants – who often need to learn a new language – to have a lower dementia risk. In fact, the opposite is true. Several studies have found migrants face a higher risk.
The reasons are complicated. Poor health, social isolation and depression, particularly among migrant women, may all play a part, sometimes linked to limited language skills stemming from a lack of education.
This suggests that being able to communicate well enough to express your needs and get support may matter more than simply speaking another language.
Indonesia has the largest multilingual population in the world, with more than 200 million people speaking more than one language. Yet dementia rates in some parts of the country are double those in wealthier western nations, according to research my colleagues and I conducted.
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This is especially true in poorer rural areas with low levels of education, and among women. But even there, staying socially active and exercising reduced dementia risk.
If the brain reserve theory holds up, learning a language later in life could help the brain form new connections and cope better with ageing. The process also increases blood flow – and with it, oxygen and nutrients – to the parts of the brain being used. This fits with the “use it or lose it” idea, that the brain works a bit like a muscle.
As dementia takes hold, people often lose their weaker, second language first. That would explain why its protective effect on the brain fades and why diagnosis is often delayed rather than prevented.
To really test whether learning a language protects the brain, we need studies that compare older people who learn a new language with those who don’t. So far, this kind of research has produced mixed results. About half of the studies found no effect on cognition.
As with most dementia research, one thing is clear: no single habit – including learning a language – is likely to be the deciding factor in whether someone develops the condition.
Eef Hogervorst currently receives funding from the ESRC, RST, and ARUK and in the past has acted as consultant for Proctor and Gamble on diet and dementia. She is affiliated with Loughborough University and acted as expert on gender-related dementia prevention guidelines using sex hormones for UK (NICE) and EU (ESHRE).
