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........

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