(MENAFN- The Conversation) People are living longer than ever around the world. Longer lives bring new opportunities, but they also introduce challenges, especially the risk of age-related decline.

Alongside physical changes such as reduced strength or slower movement, many older adults struggle with memory, attention and everyday tasks. Researchers have spent years trying to understand why some people stay mentally sharp while others deteriorate more quickly. One idea attracting growing interest is multilingualism, the ability to speak more than one language.

When someone knows two or more languages, all those languages remain active in the brain. Each time a multilingual person wants to speak, the brain must select the right language while keeping others from interfering. This constant mental exercise acts a bit like daily “brain training”.

Choosing one language, suppressing the others and switching between them strengthens brain networks involved in attention and cognitive control. Over a lifetime, researchers believe this steady mental workout may help protect the brain as it ages.

Studies comparing bilinguals and monolinguals have suggested that people who use more than one language might maintain better cognitive skills in later life. However, results across studies have been inconsistent. Some reported clear advantages for bilinguals, while others found little or no difference.

A new, large-scale study now offers stronger evidence and an important insight: speaking one extra language appears helpful, but speaking several seems even better.

This study analysed data from more than 86,000 healthy adults aged 51 to 90 across 27 European countries. Researchers used a machine-learning approach, meaning they trained a computer model to detect patterns across thousands of datapoints. The model estimated how old someone appeared based on daily functioning, memory, education level, movement and health conditions such as heart disease or hearing loss.

Comparing this“predicted age” with a person's actual age created what the researchers called a“biobehavioural age gap”. This is the difference between how old someone is and how old they seem based on their physical and cognitive profile. A negative gap meant someone appeared younger than their biological age. A positive gap meant they appeared older.

The team then looked at how multilingual each country was by examining the percentage of people who spoke no additional languages, one, two, three or more. Countries with high multilingual exposure included places such as Luxembourg, the Netherlands, Finland and Malta, where speaking multiple languages is common. Countries with low multilingualism included the UK, Hungary and Romania.

People living in countries where multilingualism is common had a lower chance of showing signs of accelerated ageing. Monolingual speakers, by contrast, were more likely to appear biologically older than their actual age. Just one additional language made a meaningful difference. Several languages created an even stronger effect, suggesting a dose-dependent relationship in which each extra language provided an additional layer of protection.

These patterns were strongest among people in their late 70s and 80s. Knowing two or more languages did not simply help; it offered a noticeably stronger shield against age-related decline. Older multilingual adults seemed to carry a kind of built-in resilience that their monolingual peers lacked.

Could this simply reflect differences in wealth, education or political stability between countries? The researchers tested this by adjusting for dozens of national factors including air quality, migration rates, gender inequality and political climate. Even after these adjustments, the protective effect of multilingualism remained steady, suggesting that language experience itself contributes something unique.

Although the study did not directly examine brain mechanisms, many scientists argue that the mental effort required to manage more than one language helps explain the findings. Research shows that juggling languages engages the brain's executive control system, the set of processes responsible for attention, inhibition and switching tasks.

Read more: Can brain training really shave ten years off brain ageing, as a recent study suggests?

Switching between languages, preventing the wrong word from coming out, remembering different vocabularies and choosing the right expression all place steady demands on these systems. Work in our lab has shown that people who use two languages throughout their lives tend to have larger hippocampal volume.

This means the hippocampus, a key brain region for forming memories, is physically bigger. A larger or more structurally robust hippocampus is generally linked to better memory and greater resistance to age-related shrinkage or neurodegenerative diseases such as Alzheimer's.

This new research stands out for its scale, its long-term perspective and its broad approach to defining ageing. By combining biological, behavioural and environmental information, it reveals a consistent pattern: multilingualism is closely linked to healthier ageing. While it is not a magic shield, it may be one of the everyday experiences that help the brain stay adaptable, resilient and younger for longer.

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